This is only a guess, but as covering the nose makes them pause and then breath normally, I would imagine that going unconscious would have the same effect. I've never heard anyone mention losing a dog this way and I've been in touch with hundreds of owners.
Joly had an unpleasant experinece a few weeks ago; his own fault. While some grass was being strimmed, he started snaffling it and ended up doing the sneeze, which took longer than usual to subside.
Later that day, he ran downstairs, behind me, then started to sneeze, normally, but could not stop; reverese sneeze remedies not working. Just at the point when I was beginning to think I'd need to ring the vet for advice, I noticed a tiny piece of grass, on the tip of his nose. thinking that this was the cause of the tickle, I went to flick it away, only to find that it was about 4cm long, but it came out with no problems.