Jay Hook?
I wonder if the J Hook did not disengage - so the gear was physically blocked from being selected up?
It's plausible to imagine the pilot getting distracted by the stuck gear and fumbling for the J Hook release. In this scenario he would have his head inside the cockpit - and hand off the power levers. This would be the worst time to experience a power lever creep back, or a sudden power lever closure, as discussed earlier in this thread.
It's a horrible thought - a nightmare- to imagine looking up in this situation to see you are low level, low speed, off the runway centre line and diverging towards the buildings.