I attempted to merge two threads today and the result was that both disappeared. I've searched my site high and low and can't find them. I've read a bit about a current bug related to deleting threads but this isn't the same, right? Any ideas how I can get them back?
Well that explains why you can't find the thread. Maybe you unintentionally selected the delete option after the merge. I just tested a merge on my forum to make sure it's not a bug. The thread was not deleted in my test.
You will have to go into a backup to get the deleted thread. It involves isolating the xf_thread and xf_post records and restoring only those records from the backup. That will preserve the thread and its posts. Other things like attachments and watch records are stored separately and require extra effort to restore.