If lined up not in shotgun and center snaps but doesn't touch offensive player it's no fumble.
The snap is a backward pass....it can't be a fumble until someone gains possession. If he loses possession afterward, THEN it's a fumble.
One play people get confused about is the 2pt try. If the QB muffs the snap, ANY player can pick it up and advance. If the QB gains possession of the snap and then muffs a handoff or backward pass to a back, only the QB can pick up the ball and advance it. (4th down fumble rule is in effect on a try)
The kicking game and try for point have their own set of rules within the rules.