Tough one, if all they did was check the population reports it would look like it's the only one. I have a common like that, SGC 80 shown as the best of its kind, but there's an 88 out there. (Which actually looks worse than mine
)
While I think that would be forgivable on a cheap card- like maybe something around $20-100- I would like to think they'd spend a bit of time getting it right on a card that will sell for a few thousand. I'm sure the interns they can hire cheap could find the prior sales very quickly.
Ultimately the auction house would keep their own database to make that process quicker.
Obviously that's all just wishful thinking.
Steve B