https://www.facebook.com/help/2687943754764396?ref=comms
Which is the issue at hand.
Also, it's "100%" the banner I saw for several days last week. Make of that what you will. I didn't click it so I don't know what it pointed towards.
I just checked fb, and went quickly to my first notification. I didn't really register what the banner was until maybe a second after it loaded - at which point I had already clicked on my first notification. By that point, the banner is gone forever. I can't find any way to get it back.
It's so, so easy to miss this message.