Sigh... I suppose this is time for another Andy ruling, isn't it? Fluxx isn't supposed to be this complicated!! : )
Maybe not, and as noted it's usually fine to play more casually, but for those times when it matters: the Action card goes on the top of the discard pile after the Action is fully resolved. Ideally it would hang in the air magically until everything relating to the Action were completed, then delicately land on top of the discard pile.