Outlook express 6 deleted emails!

If ever I needed an experts help, this would be the time.  Our email is pop3, we use either outlook, outlook express or thunderbird to pull down the mails and read them.  The user in question uses outlook express..  He doesn't back up (I know, I know), or save his mails somewhere else, just divides them in to folders within outlook express.  Yesterday, when shutting down, outlook express prompted him to compact his folders, which he dutifully did.  However, now his inbox is missing all mails from September and October up to today.  Is there any way at all to find where the mails have gone or undo the damage that OE appears to have done?  I know they should be backed up, on a mail server etc., and we are looking into it (had a meeting on it this morning before I heard of this, ironically enough), but its too late for that now.  Please help if you can, this is an extremely bad situation!