It seems the detachable towballs also have a bit of a black market going on, Someone I know has now lost 2 as whilst they lock in place, the key is the same for all of them. He had been leaving it installed on the car whilst shopping and come back to find its been pinched twice now. Replacements sourced from facebook marketplace (probabbly sourced from supermarket car parks at a guess). After having 2 the 3rd one is now welded to a piece of chain which is bolted to the towbar, defeating the point of having the detachable towhitch in the first place. I'd have though the easy solution was to remove the hitch when not in use, but that seemed too simple a solution for him!