In the eyes of the law you have rights as a buyer or consumer even for second hand goods, especially cars, unfortunately most people just accept/think they've been ****ed so carry on accordingly.

Like Hans said, it was sold as working but in fact delivered broken, it doesn't matter that Beau didn't realise till the seller had disapeared over the horizon. A purchased item should be fit for purpose and that is the basis of trade law regardless of the sale format.

If things were done properly then a receipt should've been written out, with a record of anything worth noting plus the mileage on the odometer. Beau could have paid a fee to an inspection engineer including the difference in mileage on the odometer and no doubt they would have deduced it has in fact been broken for longer than a 50mile trip and a few minutes at idle, then an ombudsman could have taken it from there, small claims court if necessary, Beau wouldn't be out of pocket then at all.