That's the darned thing about these things. If it happened in an almost explosive way and unless someone had a video camera on the model at the time it's REALLY hard to determine what the course of events truly were.

However there is no doubt at all that with ailerons that wide and since they would be fairly heavy towards the rear that they would be highly prone to flutter once "let loose" by something like the control horn breaking loose from the mounting. Once that happened the aileron moving in rapid flutter would act like a boost tab to get the wing twisting violently as well and things would lead to failure within a very short period of time or shake with such violence that the model could well lose control or break other items loose from the violence.

....And that leads us here were we can all gather around and guess at what may or could have caused it. Armchair analysis at it's best.... Tytor, aside from being sorry about you losing the model only you are in a decent position to try to choose which possible cause may have the highest possibility of being the real cause. You WERE there after all. Best of luck with a replacement and whatever happened don't do it again....