This has already happened to me, it is getting pretty common around the Twin Cities here in Minnesota. My fiance was taking my truck to the park-n-ride where she would then take the bus to work. Somebody crawled under the truck with a battery powered sawzall and cut the exhaust pipe in fornt of the cat and almost through the pipe behind it. Something must have scared them away before they could finish since they didn't take it with. I didn't realize anything had happened until I was driving down the road and all of a sudden my truck got real loud. I thought my exhaust had just come loose until I went under the truck and saw that it had been cut.
They target any vehicle they can crawl under in a parking lot. A couple of times a month the fiance says someone will get off the bus, start up their truck and it sounds like a harley. I have heard of people now having the VIN # etched onto the cat so that the recycling centers can run numbers if they think it is stolen.