He'd only seen Meg briefly. One brief look was all he needed. The skin was a pure paleness that he barely recognized. The pale and human face of a woman he technically had never met. What would that woman even say to him? Cas had never thought about that before, never thought he had to. Even know he didn't think about that woman, she was meaningless compared to the thought of what could have happened to Meg. Meg was apparently gone. She'd had that body so long he thought it was comfortable and unoccupied. She wouldn't leave it unless she had to for her own safety or she was forced to. If there was something dangerous she would have brought it to the Winchester's. Which meant someone had forced her to leave that body and there was only one person who would.
Face tense with a growing anger Castiel had marched straight to Dean's room. With the room key they had given him, he gained access to the room and was fortunate to find Dean. Anger had long ago clouded his thoughts, "How could you?" He shouted into Dean's face, "How dare you do decide this all on your own."