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. The data is lost again, and this time I end up with another 4 seconds of malus. I took a screenshot of the victory screen (quite crushed, presumably because I have it in fullscreen for the gameplay), which is attached.