Happens a lot.
High end marketeers like Sotheby’s, Barret-Jackson, et al, go to great lengths to verify ownership AND PROVENANCE. If there are any ‘holes’ in the history, NO SALE.
As ALWAYS: CAVEAT EMPTOR................
Yes, “let the buyer beware” is still good advice. Had to suck for that father and son that did a full on restoration for that Mustang. I wonder how much they lost out on with nothing to show for?