I knew someone who had it happen at his office either ca. 1995, in Oslo.
It was very much not a proper server room, which made it more understandable that they'd not realise there was stuff there that shouldn't be turned off.
I suspect there's been plenty of real-world incidences of stuff like this, and that many have never been noticed.
I've certainly pulled the wrong cable myself a couple of times over the years, even after thinking I'd been very careful, and being aware that I was dealing with servers that should stay up.
It was very much not a proper server room, which made it more understandable that they'd not realise there was stuff there that shouldn't be turned off.
I suspect there's been plenty of real-world incidences of stuff like this, and that many have never been noticed.
I've certainly pulled the wrong cable myself a couple of times over the years, even after thinking I'd been very careful, and being aware that I was dealing with servers that should stay up.