I was a reviewer on a PR that I initially approved, but changes were made and my review was re-requested. This somehow made the PR disappear from all sections on my dashboard - it's not in Needs your review", "Waiting for reviewers", "Approved", or "Waiting for author", even though it needs my re-review... So I completely lost track of it. Is this expected behavior?

That doesn't sound right - sorry about that! Feel free to share a PR number here or over DM