To sum it up: I was on my first tier 2 clockworks run and, seconds before my party reached the lift from a (rather nasty) compound level to the clockworks terminal, I died holding off a swarm of monsters that was attacking them and didn't do anything about it until the lift descended. Despite this, when I reached emberlight I was awarded "silver survivor!" If this isn't a (rather amusing) glitch, I don't know what is!
So you died, but didn't revive. Maybe the condition that nullifies the achievement isn't death itself but reviving after it.