[Buug959]

That sucks! The bastards probably saw you on the street and followed you until you parked. They were under the car as you entered the building. They also have likely stolen enough of them that they figured out that the pipe outboard of the flanges is just a tiny bit thinner and therefore cuts a little quicker.
I agree that too often the judges are either too lenient or they don't have sufficient scope within the law to be an effective deterrent but the scrap dealers that buy these obviously stolen cats have to be held accountable too. They are profiting from these crimes as well and I'm pretty sure that profiting from crime is illegal in most places.
I hope you can come to some arrangement with your insurance provider so you can keep your baby on the road. Have a better day and Happy Birthday.

P.S. I don't suppose there is any video surveillance of the parking lot that may have caught them in the act. Have you checked with the building management?