I may have missed it, but I don't see anywhere in that linked article that mentions bullet proof windscreens... and Wikipedia for the aircraft also makes no mention. Plus, we're not just talking about this particular aircraft in this incident, but generally all aircraft.

But, I would not be surprised it was tried, particularly with WWII era machines. There's very little actual benefit to having one on any aircraft, even CAS aircraft. A modernly restored version meant for airshows and racing probably would have replaced it for something more modern and lighter weight.