Played a Band of Misfits as a Guide. Sat on my tavern mat the whole game, was not allowed to call it. Is this expected? Are cards on the tavern mat in play? Should be a Guide until it leaves play....
Yes, that's correct. The tavern mat is *not* in play, so the Band of Misfit/Guide became a Band of Misfit again, and Band of Misfit has no ability to get itelf out of the tavern mat.
So as a general rule: Using copy cards as reserve card is not advised.
Only realisic exception would be if the +$4 you get from Overloard as Wine Merchant is giving you a big advantage.