It certainly can happen.  I once had Windows spontaneously rename it's .ini file with $%^* and completely disable my machine. Though the Microsoft techs were quite boggled they did confirm that spontaneous events like that can happen. There can be 'ghosts' in the machine.
In this case I could have sworn I didn't touch a thing but it being me sitting here in front of the monitor, as the fellas state above, I'm the most likely answer.   But I certainly am keeping a sharper bead on my settings now to see if it happens again.

M