How could you prove I was pretending? I could just say I exercise my powers in mysterious ways...Yes. but we could collect evidence and then find out that you were pretending, and the tests would be fucked.
The basic point is that believing in god is no different from believing in leprechauns. I don't need to provide evidence to dismiss a claim that has no evidence supporting it. Not to mention that god is an inherently unfalsifiable concept. What set of physical circumstances could possibly disprove the existence of a god? What experiment could we design to rule out the existence of a god?