I’m so sorry. That must have been pretty traumatic, especially with your daughter riding.
in the early 90s, I had a lovely 9 year old go by a likely aneurysm (no necropsy, but the vet thought aneurysm). I found her dead in the field where she’d never lie down on purpose, and with no signs of kicking or struggling on the ground. it appeared that she just simply dropped dead. She was perfectly healthy, had gone on a trail ride the day before, and was eventing regularly. I guess I should feel lucky it happened in the field and not when we were away from home. It took a while to get over it, but I did end up buying more horses after that, and nothing like that has happened since.