i've seen it before. I remember i was working at my first vet hospital and this lady walked in carrying her shih-tzu with its eye totally hanging out of the socket!
i was totally unprepared for this and like most peopl here have never even heard of this happening. Well the shih-tzu was still as happy as can be, sitting there licking his own EYE. totally weird. the doc popped it back in and everything was fine.
i've seen it again while working at other hospitals and it didn't freak me out, but that first time totally blew my mind.