depersonalization and derealization are not uncommon experiences of dissociative disorders.
I've had the huge moments like your saying and also the small ebarassing moments. . .like the time in the grocery store when I was filling this guys cart with stuff because he looked enough like my husband- who was in another isle- I mean i had a basic knowledge that i was with the guy with the dark hair and beard so . . . anyway it was not a big arrestable offense to contribute unwanted items to the other guys cart- probably thought I was hitting on him.