Just an observation. It may or may not have some bearing on your balas sudden freak out moment.
I have 3 balas, they're about 9-10". Up until recently they were in a 180g and they'd often just throw a wobbler, as yours did. Since putting them in my new 360g fibreglass tank I haven't heard a whimper out of them, nor indeed my tinfoils and chalceus either, which were also very skittish at times.
I don't know whether it is the extra room that's totally chilled them out, or the fact that, unlike a glass tank, there's only one viewing panel in my new tank. Maybe they feel more secure that they can't see as many shadows passing the tank etc, which would freak them out in my all glass 180g.
Sorry for your loss by the way, it was a nice looking bala.