> time didn't exist before it happened

Do you see what's wrong here? If there was no time, there could be no "before". Besides, if you are talking about probabilities of something to occur, that means there was some cause of that event, and that in turn implies there was time before time started (?) because causes and effects occur in time.

These things have nothing to do with the Big Bang theory anyway, let alone all this kind of speculations make little or no sense.