'Sounds like the previous owner has misplaced the "key"--
if there was a "key" involved.
Check the trunk floor, under the seats, or in the glove box. Let's not make it easy for casual, yet costly theft.
On my boat trailer, I welded two opposing chain links to the inside of one wheel. When I parked the trailer, I'd click a padlock on one link, while attaching it to a short chain welded to the trailer.
The thieves may not notice as they tow it off, but they'll be leaving a trail!