just because someone 'touches' an asset does not make that asset his. IP can and eventually probably will be replaced. but even if he isn't it does not matter for it is a team project and he does not have exclusive ownership of anything.
If he really gets uppity about it all that will do is provide encouragement for his work to be erased and replaced. oh, and it also means that he can (if he has any intelligence at all) not put this project down as a reference for actual professional work, because, well professionals don't do this and it's a big flashing neon sign that reads 'don't hire me', it'd be like putting down 'CEO of Enron'.
and I believe this episode proves that it's never a good idea to let a primadonna last any longer than their first outburst, the longer they stay the more crap they can get involved with and use as leverage.