I was thinking of the argument from divine hiddenness. It's not just that God is literally nowhere to be found, but that all the reasons to believe he's real are ambiguous at best.

I believe I address your last question in this very article. Nothing can convince a skeptic that God exists short of personal trauma or a time machine that enables the skeptic to return to childhood and grow up in a religious family that indoctrinates him or her. That's how theistic belief is generally acquired. The apologetics is ambiguous at best, preposterous at worst.