I was going to say it was the real world equivalent of, like, Redwall, or one of those other fantasy books where an event happens once a year when the sun shines in exactly the right spot to illuminate some secret writing.
I know someone who had that happen to a server he was directly responsible for (well, someone unplugged it anyway, might well have been someone else in the office - it wasn't exactly a proper server room)
It was not just that the server crashed, but the ventilation proved to be bad enough that one of the SCSI drives (which should have been in a RAID, but wasn't...) wouldn't start.
They ended up opening it to try to kickstart it manually (been there, done that myself; had a drive survive 6 months with me "helping" the motor spin it up every morning; yes I backed everything up very regularly during that period), finding the drive head had gotten stuck to whatever material covered the plate. They ended up putting the drive in an oven while connected, and heat it until it spun up, and which point they dumped what data they could.
I opened mine up, so I'd start rotating the platter by using my finger to start spinning the centre.
Of course this was with a 20MB hard drive - the sensitivity to everything from dust to alignment changes was magnitudes different from the internals of modern drives...
I thought it was an urban legend and then somewhere in 2005/2006 I first spoke to one guy who claimed it was a bank in Tønsberg, Norway.
Later I worked with a IT manager who also confirmed it was such-and-such bank in Tønsberg. I have forgotten the name of the bank but I am still on friendly terms with him so I could ask next time I see him.
(My first draft of this post said that the first bloke had claimed to be in the room, but this is 15 - 16 years ago and the next story is also close to a decade ago so I might have mixed up who said what.)
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.
Something similar actually happened somewhere I worked.
There was an outlet in the hallway, right outside the glass window looking into the server room... you guessed it -- plug in a cleaning machine, blow the fuse, take down servers...
It is reported in the book Absolute Zero Gravity, about having happened in a military context, while others here mention a bank: the only reason to believe it may have happened so infrequently that some call it a urban legend is that in the past that infrastructure was rare. The rest - failures in the workflow of instructing and monitoring "innocent" personnel and contractors - is an "overly" normal factor.
I had a root cause once that was a cable draped across the corner of a ventilation duct.
The duct would vibrate when the air was on, and the corner was pretty sharp, which caused the duct corner to 'saw' its way through the cable's insulation over time.
Took a while to isolate the problem to 'its between this box and this box' but was a pretty quick find after that :)
