Is it possible to restore a folder (in Document Library) deleted from Recycle Bin after SP1 upgrade? The folder was definitely present but vanished after SP1 upgrade. There are no traces of it in Recycle Bin also.
Have you check both recycle bins, default recycle bin and the site collection recycle bin? And how long ago was it deleted? It's possible that based on the configuration of the recycle bin that it's been deleted long enough that it met the retention date and was removed.