This is probably an incredibly silly question, but I can't find the answer to it anywhere. If an opponent knocks out one of my Pokémon, and they forget to draw a prize, are they entitled to it if they remember later?
Technically yes. It is the responsibility of BOTH players to make sure everything is done correctly. If you spot it and he forgets you can BOTH get a warning in a tournament if you don't catch it.
Source: WotC Chat (2000-08-17)