why does every developer have a moment when all his renderings on a computer mysteriously disappear??? and it ALWAYS hapanning before release date!
In this case they didn't disappear, they were never there in the first place, since the render batch job was interrupted.
It seems you haven't tried to give your Windows PC some huge batch jobs that strain your hardware (and especially your graphics card(s)) to its limits and takes days to finish?
Otherwise you wouldn't ask questions like this.
And most of these devs haven't done things like this for years in a row, they have almost as little experience with this as you do. They learn from these failures and usually the same thing does not repeat. Which doesn't mean that something else won't happen that interrupts or destroys the work.