That as with the unicorn, absence of evidence is evidence of absence.
That we have even less reason to think gods exist than unicorns exist; since if we encountered a unicorn and had a virgin to hand, we could ascertain whether it was a unicorn or not; whereas we're not even told what we're looking for when looking for gods.
That the world behaves exactly as if the only place gods existed was in the imagination of particular individuals.
That all in all we would err were we to give gods the benefit of the doubt unless we gave unicorns, Dumbledore, Santa and the Flying Dutchman the same benefit.
(All of which observations I'll gladly lay aside if someone comes up with a useful definition of a god, and follows it with a satisfactory demonstration of a real one.)
Yes, I can see what you're saying, although it's different when it comes to claims regarding actual phenomena which can be investigated here on Earth. We have the means to investigate.
I can't really say much about unicorns, since I'm a bit fuzzy on legends and myths involving unicorns. I don't think anyone has found any evidence that unicorns ever existed, but if they ever did once walk the Earth, wouldn't there be some bones or fossil record (just as we have with the dinosaurs)?
As for Santa, again, that's another phenomenon which is said to be on this Earth, specifically at the North Pole. Humans have been to the North Pole and explored the Arctic region extensively, and no reports or sightings of Santa or his workshop.
But with claims about God, it is said that God is somewhere up in the sky - in outer space. We haven't gotten to the point where we have the means to do extensive space exploration. If someone said that "God" is on some planet in the Andromeda galaxy, then someone would have to go up there and check it out to verify the claim. We can't do that yet, so we're left with an open question that can't be resolved.