While planning what to do about Lucifer running loose, Rowena tells Crowley that Lucifer can't be returned to the cage while he's occupying a vessel, however, that's exactly how "Swan Song"(season 5, episode 22) ended. Sam, while occupied by Lucifer, jumped into a portal opened by the four Horsemen's rings and took Michael who was using Adam as a vessel with him, sealing both in the cage while still in vessels. As of this episode, Michael was still there, still within Adam's vessel.