Well I'm less than happy. I spent about 30 minutes working on a post and I made a copy-paste error so I naturally typed Ctrl+Z. It erased everything I had created and apparently there's no way to undo it... fortunately I have an older version of it saved in a text file on my laptop.
Sigh, I'll try again later, but hopefully this posting helps others avoid the same experience.
Ctrl+Z is the undo keyboard shortcut in Windows, but this error can be overcome by using the Ctrl+Y keyboard shortcut to redo the change. So if you accidentally hit Ctrl+Z, then hit Ctrl+Y to correct it. This isn't a browser or web site-specific issue, but general Windows operating system shortcut.