Sounds like the guy just didn't know any better, which honestly happens more than people want to admit. A notary stamp on a title isn't some magic trick, the bank or the state needs the seller's signature to match, and if it doesn't, of course they send you back to the end of the line. Maybe he thought having a stamp period was enough, but the number on it is right there in plain sight, so it's kind of on him for not checking. I get that the DMV is annoying, but this isn't some deep mystery about window 6 being cursed, it's just people not reading the paperwork.