You're kind of playing with words. You can prove that someone is wrong or that something is false. It has the same meaning as being able to disprove a claim, in fact, here is one online definition of disprove: "to prove to be false".
but I am unsure if you meant all that in terms of you can't say it in wording or if you couldn't get the proof. So I'll leave it there.
The burden of proof does not rest with the Atheist. It is not necessary, to an atheist, to disprove god anymore than I feel the need to disprove that there is a invisible dinosaur sitting in front of me.
Religion is what is asking for your faith, not atheism, and for that reason and because the nature of the claims, the burden of proof relies with the believers. I know the silly way you can try to reverse this, lets not bother.
So, assuming no one on earth believes in religion, then there isn't anything to prove or disprove anyways. It's irrelevant.