Well, luckily I didn't do anything major that I wasn't able to reverse, but I can see this as being a SERIOUS issue.
I wanted to change the "Keyboard Encoder" link to something more generic, and do a finer sort from there. I went to edit the keyboard encoder page, and didn't realize just simply changing the link on the main page didn't change the page name itself. Blip! The page "vanished". Reversing my changes had everything working again until I could figure out how exactly to change the link AND page name.
I'm thinking LOTS of information could be lost this way, and there might be the occasional someone who changes LOTS of stuff at once and can't backtrack his steps like I did.
I'm too tired to contemplate solutions right now, so I have nothing to add other than "there it is"