It's true that all beliefs are a leap of faith to some degree. I would have difficulty stating a belief that "there is no fly in this room" simply because I have not detected it. I am fly-agnostic.

It is also however true, that we can dismiss without proof anything that is alleged without proof. If you tell me there is a fly but I cannot find it, I need not subscribe to fly-agnosticism to presume you were mistaken!