Yeah its never happened to me before. I know the cpu has hit the field goal post and missed the field goal in some of my games before but its never given the ball back to the cpu. Maybe its only the cross bar that does it?
If you have a player under the goal post and he catches it coming off of the goal post, the your opponent will get the ball back. I've tested this a couple of times. One was in my FIU dynasty, and my opponents kicker hit the goalpost on the XP, and one of my players just so happened to catch it. I ended up having to kick the ball off to the CPU.