If true, the question was probably asked as what to do once there, not if they should go to the ball in the first place. So the Rabbi may have been “forced” into given a heter, if that’s possible.
Legitimate heterim to be driven home by car are also given when one is forced out of the hospital, rather than spending many hours in the lounge or wherever on Shabbos. But then there was a NEED to be there, and part of the reason is probably so one shouldn’t hesitate to go to the hospital for a ??? ????. Or when someone is released and not fully by the kochos to walk yet, and a hospital waiting room is not the best place to recuperate.
But as I mentioned in the other thread, I’m really bothered by the scenario you outlined, and even with a heter it’s definitely not in the spirit of Shabbos.