I remember one person on this forum saying it happened to them and that the chip traveled along way, got stuck and never caused an issue after that. I don’t think there ever was any medical evidence of any of it and I can’t find the thread.
It’s almost impossible if you install correctly though. Pinch & poke with the needle parallel to the skin. After breaking through the skin there shouldn’t be any changes in the force required and there shouldn’t be a large amount of blood either
If you’re really worried about veins you could locate, mark them and avoid them. Maybe use one of those vein viewers.
Edit:
I found it, judge by yourself: