It looks like what happened was that you deleted the parent area you mentioned, but none of the sub-areas below it were deleted, so they and the pages in them got lost in limbo. This is possible if the childlist for the original parent area was corrupt. If this was one of the first areas you ever made and you made it in Alpha or early Beta, I could see how this might happen. But after Beta 5, it should not be possible to generate corrupt childlists anymore, and the upgrade script at Gamma 3 should have regenerated them flawlessly.
At what point did you delete the area in question? If it was prior to Gamma 3, I can understand what happened and I can write an upgrade script to handle this case. But if you deleted it since upgrading to Gamma 7, I'm at a bit of a loss as to what caused this in the first place...