Potions of stun recovery are potions that are supposed to help the PC recover from stunning. However, stunned PCs cannot drink potions to begin with, making them useless (more useless, in fact, than the potion of uselessness). Presumably added to the game as a joke, same as with the scrolls of cure blindness and literacy check. Throwing a potion of stun recovery at a stunned monster does not cure their condition, which may be a bug.