By any chance is there a DEV or test server having a copy?
If they were deski reports then check this link Accessing reports that have been deleted in InfoView
or if they were webi reports which might have been created or modified in Rich client then check for a copy on local drive. Try to replicate the above steps as in Deski and see if it works (though I havent tried that yet)
And of course the more laborous way is to use your CMS repository & FRS backup done recently.
For auditor part see below link, ask your query there or do further search on BOB who deleted a public folder?
edit: checked a webI report by creating it in Rich client and exporting, then deleting from Infoview. You can still open it from Rich client from local folder and export back
haider 
(BOB member since 2005-07-18)