This happened to me once. I thought I was doing ctrl-Z inside of an app I had been using up to a few minutes earlier, but I hadn't realised that instead a File Explorer window that was currently highlighted.
That was my first thought when reading this: how about accidentally having explorer focused when pressing ctrl-z... Good lord. Usually Linux is more on the rough, "you're a power user so you better never make mistakes" side of things, but according to that other comment, KDE's Dolphin really nailed that scenario.