There's a program called Disk Investigator that shows stuff that's been on your hard drive that you might not realize was there. It's a longshot though.
What is Disk Investigator? - Disk Investigator helps you to discover all that is hidden on your computer hard disk. It can also help you to recover lost data. Display the true drive contents by bypassing the operating system and directly reading the raw drive sectors. View and search raw directories, files, clusters, and system sectors. Verify the effectiveness of file and disk wiping programs. Undelete previously deleted files.
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