If the parking brake had been set during push, its likely the sheer pin would have sheered and the tug would not have been able to tow it back to stand without a new bar.
I had a tug stop after the push back and suffer a hydraulic problem. Couldn't disconnect the tug from the bar, which is the sensible thing to do first. It was an Airbus 321, and unless the tug disconnected first, ground crew were unable to disconnect the bar from the nose wheel. After 10 minutes on the taxiway we were instructed to be towed back on to stand to fix the problem there as we were causing an obstruction
