In an Airbus looking at the FMA should be second nature, it is neither an abnormal nor an emergency procedure. In this case it would have been obvious that the autopilot was not engaged. And yes, I have had an unexpected high altitude upset that tripped the autopilot after 5hrs in the cruise on the return to UK non acclimatised.
BEagle as an ex QFI and Captain you understand the importance of knowing who is handling the aircraft. In this case both pilots were. In my case the FO was, I assisted him.
Was I lucky? More pertinently, was I lucky to follow procedures?