Saw that as well. May make a formal announcement of closure (possible, they may not have enough keys to keep it going), or it may just be to indicate when it is or is not going on without people needing to go to the page.
Not sure if anyone else got it, but it annoys me mostly because it was the first time I'd ever finished it.
I'm mostly pissed off that I still got a Malus without getting a key. Can't provide much more than the attached pictures.
Happened twice actually. Both were on the Mining Challenge. The first time, I had clicked off to another page for a second before the challenge finished. Makes sense, and nothing came from it, key or malus. Second time, finished it with an 8 second malus, and watched as the timer ticked down...
Completion for me relies on what challenge I end up getting. Archers is the worst, as they each require three hits and run off every time you get close. The lack of an ability to see what the keys offer is also annoying, as many prizes I would almost rather they not end up on my account, for...