I don't know why you guys think Kisame is in some kind of debilitating coma or something.
My assumption is he's hiding inside Samehada for this very purpose, and I don't see why he'd be all weak or anything when he finally decides to come out.
The explanation they gave for why Kisame can't be detected is because Samehada has the same chakra signature Kisame does. People can sense Kisame, it's just that they assume it's the sword that they are sensing.