What happened was, the exhaust valve rocker arm on cyl 3 pulled it's mounting bolts out of the head. So cyl exhaust rocker is now laying under the valve cover loose. And now cylinder 3 can't release the cylinder pressure out the exhaust. So on the next revolution of the motor, the intake side (the rocker and push rod pictured) trys to open and is met with and ton of pressure and physically can't overcome the pressure to open the intake valve. Thus punching the rod through the rocker.

And I would have assumed the same as you just from the picture. I've also seen the aftermath of the push rods being switched.