I can also say that propmasters are not 100% correct. I have a couple situations where the Propmaster said "no way" but I can send him a screenshot to prove otherwise. The reply is always, "man I don't remember doing that!" or "how did that get in there?"
Regardless of whether it is or isn't a screen used piece, I have to agree with Mic on the dismissive attitudes. Instead of staying on neutral ground or even considering the fact some crew member slipped a promo or replica on set and it actually became screen used, you guys immediately call BS. Wait for the movie, try and help him find an oddball promo ring stuck in some scene. If you don't, then Mic can go back to his friend and call BS while you keep your trap shut and be satisfied you helped him without criticism.