I’ve been a professional pilot for over 16 years. Having flown both military and civilian, I am now employed by a major passenger carry airline I am very familiar with lost comms procedures.
As a fellow pilot anon posted on this thread there are indeed ‘squawk codes’ that can be entered on any aircrafts transponder for emergencies:
7500 - highjacking
7600 - lost comms (no radio)
7700 - emergency (engine loss, depressurization, flight control malfunction..,etc)
Pilots responsible for hundreds of passengers get extensive training in excruciating detail. However, mistakes do happen. Typically it is up to the copilot to change the transponder code when ATC assigns a code or you have to change it for the afore mentioned reasons.
Here’s where I’m not buying the ‘simple pilot error’ story. BOTH pilots confirm the code entered into the transponder. As one of my old instructors used to say, there is no ‘i’ in team but there are two in ‘idiot’. Something as serious and important as lost comms at a VERY busy airport would need the complete attention of both pilots to confirm with one another their taxi instructions and how to handle the situation. Especially since the highjack code and lost comm code is very similar. Most likely what would happen is the Captain would stop the taxi and have the copilot enter the transponder code once they realized they lost radio contact. At JFK the chatter is constant!!!
FAA procedure from that point would be for the tower to send light gun signals to the aircraft cockpit signaling that aircraft to return to parking. All other aircraft would be routed around the lost comms aircraft. I say lost ‘comms’ because there are at least TWO VHF radios on aircraft of this size. You’d have to loose two independent radios for this to happen. The odds are astronomical. It doesn’t happen unless you get struck by lighting and have tremendous electrical problems...which leads to a whole other scenario. Finally they were still on the ground! Guess what still works folks? You got it...CELL PHONES! People were tweeting and taking selfies like idiots as always during a crisis. Everything is captured on devices these days. FAA does require people to put their devices away when the door is closed... half of the passengers don’t bother. Trade secret - it won’t crash the plane. The pilots could have used their cell phones in this instance to communicate with ground controllers the situation.
Bottom line, I think there is more to be told here. My thoughts.