Sorry, but the company would still fire him, because just because he doesn't believe it was fake, he should have known better or been suspect.
Excuses like that don't work in today's world.
As for what could go wrong, the police are generally called because it can be construed as a felony, violation of rights, or attempt to steal (it is considered theft by some law professionals).
Normally you also receive a type of probation at the end of the sentence, and generally a fine of some sort, perhaps some jail time depending on age.
It's serious, and it can cost you a lot, as well as the job and some times fines and black marks on the other person.
Learn something from this, please.
- Del.