ipod wont go into dfu or recovery mode

Hay guys my friend stole my ipod a few weeks back and i finaly got it back but it had a lock on it and i cant figure it out for the life of me. ive tried putting my ipod into both dfu and recovery mode but nether one of them will work is there another way to restor it? it wont even notice itself as a disk drive or show up in my itunes so i am lost compleatly pleas help