There I was, working away, and all of a sudden, my work starts scrolling at a furious pace and disappearing. You know that face the kid makes when he splashes on the aftershave in Home Alone? That was my expression exactly as I desperately tried to make it stop. I couldn't.
I don't know what I did to cause that. I probably hit the wrong key, but darned if I know which one or what sequence caused that to happen. Fortunately, I was able to just go to "undo" and undo.
Also fortunately, what I lost was the unrevised portion of the chapter. Still, it was traumatic watching my words disappear with such speed and not knowing how to make it stop.
This would be why I always make a separate directory for each draft and save my work each night, or whenever I stop for the day.