Oh... I see what it's about. And I agree with many others- some in his congregation. You don't 'really' pretend to be an atheist from such a perspective.
I am reminded of Descartes decision to formally 'doubt' the existence of God. Even Descartes knew it was only a logical doubt... but the Catholic church was not amused, and Descartes spent some time backing down.

I'm not sure what kind of 'sign' this preacher expected in his year... struck by lightning? A visit from some angels?

Now.. I personally knew a Unitarian minister who started as a Southern Baptist. He explained that he "..woke up one morning realizing that he could no longer get up and spout the standard line."
He still was concerned about 'issues', so he became a Unitarian. His change came from inside... not some cloak of a test.