Don’t panic. You could recover your data back as long as you take the right steps.
1. Do not save new file on the same drive in case of data loss.
2. Download a pen drive recovery freeware
to regain your data. This application was helped a lot as the external hard drive of my bother became inaccessible. At that time, I was there. This freeware surprisingly retrieved all his files back. You could give it a chance: http://freeware-fix.blogspot.com/2013/03/external-drive-data-recovery.html
3. Save your recovered data on a different drive in case of recovery failure.
Note: You should always remember to back up your important data in the future.