Was the lock/locker destroyed? Or did there appear to be no signs of forced entry? If that's the case, then it's someone with your combo, if it was actually broken into, then sounds to me like you've got some really determined scumbag who's probably already sold it for drug money by now. No joke either. Happens at my gym lockers all the time, every time I go to school someone has gotten into my locker and stolen my pants, I just don't even keep them there anymore.