Gadreel. Gabriel doesn't even have to hazard a guess in that regard. Dean never let the angel out of his sight, even after it was clear that Sam was alive and Gabriel could help keep him that way. He didn't know as much about the Harvelle women, but sneaking into an unguarded Heaven wouldn't be that difficult. "That poor bastard. Locked away all this time away from him."

"They need her back. Dean and his angel."