Get a hacksaw blade and and with it in the "backstroke cut" position, grind down the top on one end til all that's left is very little metal and the saw teeth.
Insert this cut down end on the side of the key that has the teeth. The idea is to get the hacksaw blade teeth to engage the key's teeth. do this carefully and the sub should come out. It doesn't hurt to lubricate the lock with WD-40 before trying this.