[Faize's attack dog would wag his tail if he could. Did he do good, Faize?? Are you proud.]

That's... the only thing that makes sense, the more I think about it. If Inaba's certain within a reasonable doubt that the rock wasn't there, then... it could explain it.

So I guess... the question is to look at what other kinds of blunt weapons could have been used, or... someone strong enough to hit you in the head and knock you out with their bare hands.