Well, Bob was with a necromancer back in WWI, and I don't think Caspian would have been in the asylum that long. Surely someone would have noticed the age problem, or lack thereof. On the other hand, surely that's not the first time he was caught and imprisoned. Or maybe someone just plain stole Bob.

I don't know about whether Methos would want Bob back. He might feel that he has time to retrieve Bob later when Dresden has no further use for him, in a few centuries or something.