I can absolutely believe the story is true in core facts, if not this rendition. How many times have tried to turn on a light to find your flashlight when the power is out? It's just one of those things you take for granted.
I had a friend ask for some help installing a new modem. She couldn't get it working, so I suggested she download the latest drivers from the Internet. She said, "good idea, I'll try that tonight." It wasn't until she started trying to find the site, that she realized the new modem was her connection to the internet. I knew that and didn't catch it myself until she told me. D'oh!
You take things for granted all the time.
I've also had some help desk experience ... until you've worked one, you cannot believe how silly users can be.