let me put it in another way, the test says, "Whenever Mammoth becomes stunned, KO him."

it doesn't say KO Mammoth only when he is stunned, it says when he becomes stunned, so regardless if you are able to recover Mammoth, ready Mammoth, elect Mammoth to become the next US President, if he becomes stunned, he will become KOed unless you can prevent him from being KOed like using Lazarus Pit. but recovering won't stop him from being KOed.

^^^, well, unless he is in your hand or back on top of your deck. <3 Kidnapping/Reign of Terror