Some time ago, I was browsing through the history of the close votes review queue of a group and I noticed that a certain question had been closed after five users having voted there to close it (and no user voted to keep it open). I found that strange: how had that question got there in the first place? As far as I know, a question is sent to the close votes review queue only if some user votes to close it (am I right?).
Then I thought that what could have happened was this: a user voted to close the question and then retracted their vote. This would explain it. Is that the only explanation? Is it possible to know who that user was (my guess is that it is not)? Or, at last, do the group moderators have access to that information?