Ever since I earned the Rep to see the moderator tools section on the "Review" screen, I have been puzzled by what I am calling "phantom" flag notices. That is, part of the screen appears to indicate that there are flags to be evaluated-- "Posts marked as requiring attention" per the link title attribute--, but when clicking the link to take a look, there are no posts. For example...
That screenshot was taken after clicking the link marked "1 flags", but clearly there are no flagged posts on the left.
I am assuming this is a bug as I can't come up with any reason to indicate that the is 1 (or more) flags needing attention when no posts actually appear on the screen.
I should add that I have voted on a few flagged posts on this screen but the great majority of times I've tried the result is as in the screenshot.
Even if this is a cache related issue as suggested by Rarst, I still consider it a a bug, of bug-like, as what it accomplishes is minimization of the notice. I am basically at the point where I just ignore it.
There is now a "show posts you've already flagged" link on the flag page, making this point moot.