Hi,
Could it be that the pilot inadvertantly thumbed full nose up, while gripping the stick. I suspect that the audio of trim movement could well have been lost among other warnings sounds, and once trimmed full back, recovery would be almost impossible, unless trimmed back the other way.
Methink it's not "thumb trim button" on stick and methink movement of trim wheel is soundless.(that's not help but is how is that in Airbus)