Hi jcglfer, I'm so sorry for your loss. My first v died suddenly last September - literally dropped dead in the yard while chasing a squirrel. My SO was with him at the time and saw it transpire. It was very sudden - 30 seconds from the onset of symptoms to death. He was only four, and had just had his annual check-up with the vet (clean bill of health).
We did get a necropsy, because we have a second v and wanted to make sure there wasn't an environmental component that would mean she was in danger too. The necropsy was inconclusive - nothing toxic, no bleeding in the brain, just mild signs of myocarditis in the heart. So, best guess is it was a fatal arrhythmia.
Our breeder said he's never had any feedback from owners about anything like this happening with any of the other dogs he's bred, and iirc, the sire lived to 14+, and dam is still alive at >10 years old. We also spoke with an emergency vet who herself has GSPs, and she said heart problems are virtually unheard of in pointing breeds, so it seems to have been a fluke thing.
He'd had some mild health problems over his life, though, so I think I will never really be satisfied that I couldn't have done more for him while he was alive to at least detect that there was a problem before it revealed itself in such a terrible way.