Did you try sitting in the car and locking it with the inside lock? If it works that way, then it sounds like the door tumbler or the rod going to the door latch. If not, it's probably the door latch itself.

In either case, door disassembly will be necessary.

Hope this helps and good luck.

You could try getting a rottwieler that's been fed gunpowder to guard your car during this perilous time.