iPod Touch 2G all songs deleted! HELP!

Tried to delete SOME music videos, synced it. Box appears saying 'some music videos may be deleted, are you sure you want to sync?' I said ok. Next thing I know...NO MUSIC OR PHOTOS. ***.

How can I recover all of my song, even the ones that are no longer on my iTunes? Like from an old computer. Dont iPods have an internal memory thingy or something?