If you go to iTunes>Preferences>Devices how many backups do you see? If only the recent one you are out of luck. When you synce/backup to iTunes, iTunes just updates the last backup with the changes thus overwriting the previous backup.
If yo have a previous backup ina coputer file backup yu can restore theat backup and restore the iPod from that backup.
iTunes places the backup files in the following places:
- Mac: ~/Library/Application Support/MobileSync/Backup/