To me it feels really early but I can't imagine she'd mention it if it were not ~possible~ but it would be really amazingly small to see, I believe?
I mean: You had your IUI, hopefully things met up on time, fertilized, floated around for a bit and found a nice place to settle... but that process usually takes a few days, I believe, and then growth happens from there...
I did find this:
"The first that you can usually see on a transvaginal ultrasound (around 5+ weeks) is the gestational sac (GA). The gestational sac is a structure that surrounds the embryo and can be seen even before the embryo is visible. About 7-10 days later the embryo can be seen on transvaginal ultrasound at around 6w3d plus the fetal heart beat.
You cannot usually see the pregnancy on a transvaginal ultrasound until a blood hCG level of at least 1,500."
Have you had a beta? Did you get a positive POAS?
So, I would say is it possible, yes. And finger's crossed the tech was amazingly right!
Good luck, hoping for you!