Whenever I click on a question in /review/close, it is gone the next time I open the site, even if I didn't vote to close it. As a consequence, I now have ~200 supposedly reviewed questions and there seems to be no way to make them re-appear in /review/close.
Hovering the Hiding reviewed and closed posts text in the Your Review Stats box on the right side shows:
A post is considered reviewed as soon as you or 2 other users click the review button
That sounds like a good idea to solve this issue, but I haven't found that button anywhere. *confused*