If you didn't make a backup of the sync key then there is no way to retrieve data stored on the Sync server. The sync key is used locally to encrypt the data before it is send to the sync server and without this key your data is lost. For future prevention it is advised to backup your data locally because Sync is designed to work like a backup, but merely to sync data between multiple devices. *http://kb.mozillazine.org/Profile_backup *http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox <!-- Y29yLWVs -->