> the existence of a creator in a quantifiable way.
the meta existence of a creator, you mean? because a creator can't be fully included in its creation, if it did it would not create but simply "be".
If a guy tells you "I saw a pink unicorn and it told me he is God" it makes sense, logically. "I am" is a valid assertion made from the point of view of a hypothetical god. Its meaning is undiscoverable, but who cares.
Instead, your "quantifiable" applied to a meta world has no meaning, because existence is not necessarily defined the same way it is defined here. "Nobody in history quantified the existence of a god" is formally equivalent to "nobody in history discovered the smell of purple".