The thread you received the rep in was likely deleted. When the thread disappears, so does the rep.
JaggedEdge Reviewed by JaggedEdge on . Reputation "Comment" Disappeared! I recently got a rep comment from somebody on my "USER CP" page. It was the latest one, earlier today or last night, and now it's gone. The previous couple of comments, from other people, are still there. It's not a major concern, but I'm just curious as to how this could happen. Rating: 5