In the UK that would be covered by the "Sale of Goods Act", under those circumstances , Log Books, Manual and keys should be handed back to the seller in return for full monies or another NEW machine in exchange.
If it happened to me thats what I would have done as soon as the problem was discovered!! at the same time telling all and sundry about the Low down scumbag who was trying to con me!!
Peter R-B
Vfr