Electronics are not out when the engines quit...if that was true, when you're at the gate, there would be no lights in the tube when the engines are not running. In your example..they were not without some electrical power.
Let me clearer...one shot is most likely not a problem. Can an aircraft be brought down with one shot...very unlikely. However, one can damage an aircraft enough to cause severe controllability problems thus making the aircraft very difficult to land. Do I want to take that chance with CCW on the aircraft...no way.
Again...I agree with one poster, the likelihood of another 9/11 hijacking is very remote. That being said, for those that fly, I hope you use the same vigilance while CCW on the ground that you would use in the air.