What does the warning mean?

I found this on the Firebird....if it can be done they'll figure out how...
https://jalopnik.com/terrifyingly-comprehensive-car-thieves-forge-docs-then-1719576200
so I had the story correct. you never know when you get to my age, your memory can start confusing things, hahaha. The story did have a happy ending, IIRC. After all the publicity, the car was spotted, and recovered. I think the thieves actually put some money into it, fixing a few things, so he came out OK in the end.