I’ve seen this argument somewhere before

I think they ripped it off from a theology textbook, simply changing the name of the mystery in question: You Can't Prove There's No Cannibal Rat Ship.

Except, of course, there is a possibility that the Cannibal Rat Ship exists, and there are at least verifiable records that a ship called the Lyubov Orlova once existed. The theologians don’t even have that much of a glimmering of likelihood.