My buddy and I were discussing football in general last night, and a rules question came up which neither of us had the answer to. I am hoping some wise person here knows the answer. Situation: QA drops back to pass. Pocket collapses, ball goes to the ground, recovered by the defence. Call on the field is a fumble recovered by the defence. The offence challenges the play, claiming that the QB's knee was down before the ball came lose. The referee reviews the play and sees 2 things: 1. The ball was out before the knee hits the ground. 2. The QB was hauled down by an illegal face mask, that went onseen on the initial play. My question is, can the referee reverse the call of the fumble, and call a 15 yard facemask on the D?