One of my old co-workers claims that in a drunken stupor she forgot a $700 TITO in a machine. She said that next time she went to the casino, security guards brought her to an office, explained what happened and paid her out.
I never really believed the story... I figured that they would have called her or sent a letter, since she was using a player's club card and they had all her details... but who knows?

ETA: It's worth noting that this was in a Minneosota NA casino - not in Vegas.