This is one I can relate to directly... not as a medical opinion or to even suggest what might have happened, or what may happen... just a true story of a scary time in my life. It was four years after we had retired at age 53, because of a cancer scare.
My best friend was in the front seat with me, with our wives in the back seat... coming back from a day at Daytona Beach swimming, body boarding and relaxing. I was driving. Until then, never a serious health issue of any kind. Age 57.
No warning. No pain. I woke up with my friend shaking me... I had blacked out while driving, and we had all been talking right up until that time. They tell me they were wondering why the car had slowed down... right in the middle of the outside lane. My friend held the steering wheel, and kicked my foot off the gas, then took about a minute or so to try and wake me up.
He drove us to the hospital... where I went in for tests that showed no abnormal results, but scheduled me for many tests over the next two weeks... blood, stress, Holter Harness, MRI, sleep deprivation and some others that I can't remember. Nothing.
Final result... the experts said "sometimes it just happens".
When this blackout happened, it was after we had retired... earlier than we had wanted or expected. In a way, we dodged the bullet twice.
That was then... this is now... 25 years after retiring... not rich, but okay financially, and still enjoying and appreciating life.
We adjust... how we adjust depends on attitude. The glass is half full and there's lots more where that came from.
Best wishes for a good outcome.