This can happen even without a false grip. If the bar drifts up toward your head, the weight transfers from your chest to your front delts and you can lose it pretty quick. About 6 years ago, I was bench pressing in a meet (wearing a bench shirt unfortunately), and I had 430 lbs. drift up toward my head. The side spotters were daydreaming, and the head spotter had cleared the area so that the judges could see.
Lucky for me, I was "in the flow" and time slowed down for me. I was able to guide the bar to rest on my chin, which quickly dislocated. The spotters jumped in in time to save my life, but it wasn't pretty