Dean had his neck cut in the Citizen Fang. That mark it gone when he confronts Sam in hotel.
Usually when an angel is killed, you can see a print of their wings, after Samandriel is killed his wings are not visible.
After the man in the hospital says, "It feels like the sun just ate my face," Castiel tells Dean it's a metaphor, but that is incorrect; it is an idiom (it feels like) with some personification (the sun just ate) added in.