I encountered this Low Quality Posts review queue item on Chess Stack Exchange. I was curious who had flagged it, but to my surprise the mod timeline doesn't show a Very Low Quality / Not An Answer flag by either the system or a user. Normally, both pending and handled flags are shown there. Also, the moderator dashboard shows no pending flag and neither does it appear on the moderator's history pages. The 'Show flag history' in the mod menu is disabled as well.
How is this possible? It seems to happen more often, here is another case on Ask Different.