After some investigating the damage seems to be minimal, just the main index pages (costume, events, study, log, Titanic etc.). The biggest loss is the log archive, as there is no way I can reconstruct that, but I daresay life will go on without it.
The unfortunate event apparently occured last week when I went to download select pages from the server to my computer (my way of backing them up). Instead I did the opposite, uploading the old (backed-up) versions to the server and losing the new. Thank goodness I didn't make that mistake when backing up the diaries or Titanic doll pages - I would have died!
I guess the lesson is once again to back up files OFTEN. You'd think I would have learned by now... :>