THere is a software called free undelete that can help you recover deleted files from literally everything. Since mp3 players show up as drives when connected to a PC you should be able to scan it with free undelete and recover all the files to their original location. You can get it fromhttp://www.officerecovery.com/download/freeundelete.exe
Usage is simple. Connect your player to PC. When it shows up as a drvie launch free undelete and scan you player(removable disk). When it finishes scanning, select all files, then right click on one of the files and click recover. Hopefully your player will be back to normal.