UPDATE;
The Knight's Pistol Grip was not at fault. It was the type of rail the owner of the CZ Scorpion had or used.
After examining the grip involved in the accident, there is no question that it didn't come unscrewed from the bottom as originally suspected. The grip had been grazed on the outside by a 9mm round, enough that it also protruded to the inside, causing a matching indentation on the inner sleeve with the plastic pin used to tighten the grip to the rail. This proved that the plastic pin used to hold the grip in place to the rail was fully extended/engaged to the surface of the rail as far as it could move when the grip was actually struck with the round.
So, I thought, how in hell did that grip slide off? I decided to call the owner of the MG to see if the rail was not to mill spec potentially causing the ears to slip off on the side or if there was any type of slop in the system causing the grip to fall off. He literally hadn't looked at the
MG since the accident and a giant rain storm hit that night causing everyone to rush packing their MGs so they wouldn't get soaking wet.
This afternoon, he got back to me literally sick to his stomach. The rail system he was using had the middle part of the rail milled out along the whole length of the rail. I.e., there was literally nothing other than the very tip of that plastic pin tightened down on a flat aluminum surface preventing the grip from simply sliding off the rail. This small plastic, tapered pin was the only thing holding the grip in place. The findings point to 100% user error. The grip was not designed to work with this type of rail system at all.
Mystery solved.