Speculation can be a useful tool when applied judiciously - after all, many investigations carried out by police detectives or other professionals have often proceeded to a satisfactory conclusion though employing a theoretical approach when the known facts are few and far between. But in such cases the speculation is closely tied to these known facts and it is not allowed to venture far from them. To speculate in a haphazard fashion, or in order to try and remould the facts to fit an agenda, is at best unhelpful and at worst dangerous. Invented dialogue, such as stating "Oh yeah, I know who YOU are" is particularly risky in my view - one cannot rewrite history or turn it into a novel (or novella). This is one of the reasons why I think invented dialogue spoils "Bix: Man And Legend", which otherwise contains a considerable amount of well researched information.
In my own small way, I have delved into the Ivens case. Along the way, I have collated the groundbreaking work of others and have (admittedly!) theorised in order to try and bridge the many gaps, but I have tried to establish the known facts as far as it is possible to do so, and to not wander (or indeed wonder!) too far from them. I have also tried to remain unbiased.
Looking at the known facts surrounding the Ivens case is like staring at shards of glass scattered from a broken mirror that can at best only reflect a hazy image dulled by the inevitable action of time. Time heals old wounds, but it also obscures them. All we have in fact, in terms of anything substantive, are the two short police blotter records, Ivens' "affidavit" (Bob may want to explain why I have put this word in quote marks) and the comments from Sarah Ivens' two daughters about her eyesight.
Having sounded a cautionary note, I would like to address some specific points:
1) The garage where the incident allegedly took place wasn't a commercial garage, as you seem to think it might have been. It was a small wood-framed building at the back of the garden of Frank Goddard's property at 1830 Grand Avenue (the same Grand Avenue that Bix lived on), on the corner of Locust Street and Grand Avenue. The garage still exists, though it is in a state of disrepair.
The garage in which James L. Duncan tried to pass a forged check was a commercial one. The December 10th, 1926 edition of the Davenport Democrat And Leader reports that James Duncan of 1330 East 10th Street, Davenport, was arrested and convicted on that day for passing a forged check at the Bettendorf Garage the previous Thursday. He subsequently spent 5 days in the local County jail.
2) The police blotter record also gives James L. Duncan's address as 1330 East 10th Street; Mahlon W Bailey lived at 1105 Oneida Avenue. East 10th Street runs off Oneida Avenue, so Duncan and Bailey lived in close proximity to each other at the time of the alleged incident. That fact doesn't necessarily signify anything of great importance, other than it is possible that both witnesses may have known each other some time before the incident.
3) The police blotter states that Sarah Ivens' address at the time of the incident was 1703 Iowa Street. However, the 1920 edition of the Davenport City Directory gives Ivens' address as 1703 Farnam Street, so it is possible that the officer who wrote out the blotter report took down the wrong details and meant to write 1703 Farnam Street. To complicate matters, there is in fact a 1703 Iowa Street in existence and it, like Farnam Street, is not far from the Goddard's residence. 1703 Iowa Street is about 550 yards from the scene of the alleged incident, while 1703 Farnam Street is even closer, at about 450 yards (walking distance).
4) Preston Ivens' affidavit states that he lived at 3030 Grand Avenue. However, Ivens' affidavit was written some five months after the incident, so it is likely that the family moved from 1703 Farnam Street (or 1703 Iowa Street) to 3030 Grand Avenue within a five month period after the incident.
5) The Beiderbecke house was of course situated at 1934 Grand Avenue. This is five houses up from the Goddard residence. Go to the Beiderbecke house (street view) on Google Maps and proceed to the alleyway behind the house (just click on the left hand side of the front of the house - by the tree - and it will automatically take you there). Turn left and move down through the alleyway for the short distance back to where it emerges onto Locust Street. Look at the house over the road - that is the Goddard house. Look to the right of the house. That is the driveway to Goddard's garage, where the alleged incident took place. You can see the actual garage from this point. There is a clearer view of it if you move down to the other side of the house on Grand Avenue. The distance from the back of the Beiderbecke's house to Goddard's garage is about 100 yards.
6) There is the possibility (I have not been able to establish this) that Sarah Ivens was known to the Goddard family. Frank Goddard had a daughter called Dorothy, who was 10 at the time of the incident, as well as a daughter called Florence, who was about 18, and three sons, Austin J (Jay), who was 18 at the time of the incident, Robert, who was 14, and James H, who was 8. Bix's arrest was the sixth of seven arrests carried out in Davenport that day, so is likely to have been later rather than earlier in the day. Was Sarah walking home from school, perhaps with one of Frank Goddard's children? Perhaps she was playing in the garden of the Goddard residence after school. Remember that Sarah lived in close proximity to the Goddard property. All of this is highly speculative of course, so I am treading with caution here.
7) Connections with Bix: Frank Goddard's wife Ella (nee Finke) and her sister Agnus Finke had a cousin called Robert Finke, who loaned Bix his cornet when Bix was just starting out on the instrument. Though this has nothing to do with the incident, it does serve to indicate the close knit nature of the local community. This is further illustrated by the fact that R C Finke and Robert Finke Jr were amongst the people who attended Bix's funeral and their names are entered in the "register of friends who called at the service of Leon Bix Beiderbecke" (as reproduced on page 590 of "Bix: The Davenport Album"). Moreover, the Goddards joined the First Presbyterian Church the same year that Bix was confirmed there (see page 186 of "Bix: The Davenport Album"). Another fact revealed in The Davenport Album is that Mahlon Bailey was an apprentice machinist at Bettendorf Axle Works, where Frank Goddard was employed as a purchasing agent. However, Bob has discovered that by May 1920 Bailey was working for the Linotype Company in Davenport and was a foreman there in 1923. Perhaps he left the Linotype Company later in 1920 or early 1921 to become employed at the Bettendorf Axle Works, rejoining the Linotype Company later on as a foreman. This is just one of a number of discrepancies thrown up by researching into the case - but we should not jump to any unfounded conclusions.
8) Bix and Frank Goddard's son Austin had been classmates since kindergarten (again, this information comes from "Bix: The Davenport Album"). Bix and Austin were about the same age (Austin was 18 at the time of the alleged incident - he was born on January 23rd, 1903). In 1921, Austin Goddard was a Senior Committee Member at Davenport High School, working alongside Vera Cox, who would become Bix's girlfriend a few years later. I suppose it is therefore possible that Vera knew about the alleged incident.
I should like to conclude by stating that with the scant evidence available it is impossible to know what happened exactly on that day in 1921. There is no-one alive now who was there when it happened. What remains is an incomplete picture that is open to interpretation. Ultimately, all we can say is that a partially sighted five year old girl was frightened by something that happened to her while in Goddard's garage, and whatever caused her to become frightened may have had an innocent explanation or may have been the result of a misdemeanour.