Do you still have your backup file from before this happened? It would be located at one of the following locations:
- Windows XP: %AppData%\Apple Computer\MobileSync\Backup
- Windows Vista: %AppData%\Roaming\Apple Computer\MobileSync\Backup
- Windows 7: %AppData%\Roaming\Apple Computer\MobileSync\Backup
If you do, copy it to your desktop for safekeeping so it isn't inadvertently overwritten. Then after restoring your phone you can copy the backup from your desktop back to it's original location and it will be available to restore from. To restore to this backup, prior to connecting your phone to your computer, first disable automatic syncing in iTunes (iTunes>Preferences>on the Devices tab check "Prevent...from syncing automatically"), then connect your phone and when it appears in iTunes on the left sidebar click on its name and choose Restore from Backup, selecting the backup you recovered from your desktop. Also, you can try to extract information from a backup using iPhone Backup Extractor.