The USGA official's articulation of the rule is not what the rule is supposed to be.So this guy is saying there will be a penalty
They claimed that they are looking to penalize him because they can't see what else could have caused the ball to move. But the rule is an affirmative one, in the sense that he only gets penalized if he is deemed to have caused it to move, not if they can't figure it out and so conclude by default.
Unless they see his club hit the ball, it should not be a penalty. He wasn't even grounded at the time.