I just formatted an entire spread, and scrolled down to work on a new spread and scrolled back up and it's GONE. I saved and re-opened the file and it's still not showing up. It's nowhere else in the document. Just, poof. Apparently this has also happened to some of my coworkers. My Creative Cloud is saying my InDesign is up to date.
I'm very sorry that that event happened to you, but you're provided no information about your system, and no indication that you can replicate that problem. (I've been using and teaching InDesign since 1999 when it came out, and I've never experienced or heard about that particular problem.)
I'd start by rebooting your computer, and restore your InDesign preferences and caches (instructions below). I'd suggest that you save your files more often than you did. If you can replicate the problem, try to notice what other things might have occurred before the event happened and provide us more information: Please tell us what operating system (exactly) you're running. Please tell us (exactly) what InDesign version you're using.