The Sheet at the Expo was the series 1 sheet not the series 2 sheet that just sold on classic.
The series one sheet that revealed new short prints would be worth more.
I think it would fetch close to $50K if offered.
Yes, there is only one known first series sheet, there are about 4 or more 2nd series sheets out there.
First series sheets and or display boxes/wrappers/packs are usually much harder to find due to being put out in the marketplace first, so the sheets from the first series were used up until they were gone, then keep the presses rolling for the second series, allowing for leftovers for most second series items (packs and boxes) probably with interests fading as time went on.
The condition of the 1st series is really nice with only a slight tear at the top and not many creases, this second series had many issues, although they are all crazy rare.