I was recently (in fact just right now) browsing the review queue when I saw an off-topic question. I tried to downvote, but then I got a message that the question was deleted and I couldn't vote on it.
I believe this is a bug. If it isn't then please correct me, but I don't see a reason for a deleted question to be reviewed.
Edit: I just read about review audits, but they aren't even active on here, so it couldn't be that either.