Well, the vet agrees that if he's acting normally otherwise that it's a good thing for the plastic to come up/out and to continue to watch him.
I looked at the mat before I threw it out last week and there wasn't a whole lot missing.
I don't know what it is with this guy, he'll eat anything! Hoku will pick up a piece of rubbish or a tiny rock and spit it out and he'll go right after her and try to swallow it