Finding bizarre treasure on the bodies of fallen animals is more a trope of video games. However, it does happen in Tabletop RPGs. With random treasure tables, monsters could be found with the darnedest things: coins, magic items, potions, and even objets d’art. During 3e and 4e there was an unforgiving wealth-by-level: an expected amount of treasure required by the game for purposes of balance, so sometimes – despite all logic – a monster just had to have level-appropriate booty.

A good DM could work around this, by having the treasure in a lair, remnants of former victims. But this still required the players being motivated enough to find an animal’s home and scavenge. In earlier editions skipping the back-tracking just meant less treasure, but in 3e and 4e (because expected wealth had to be maintained) the PCs would often conveniently come across treasure of similar value in a future encounter.