lock your cars up

If the car doesn't have a VIN, stamp one in it. In two places, one obvious, one not so obvious so that you can point to it if the first one is obliterated. KA allows "Title Only" registration, so it's in your name, just not legal to drive on the street. Perhaps other states do something similar?
I know of a guy who got back his Bugatti Type 47 racer because he had done the title-only deal. When the Sheriff's dept ran the VIN it came up his and he got it back for the towing fees.

None of this will help the poor bastid above, unfortunately.