First time, I got 48/49, and the last one was nowhere to be found.
Next time I realised that by the time they turn off the lights, you have to find 10 sprites, otherwise one will be missing. So I got 49/49, but no badge.
Then I played again, 49/49, no badge.
I just completed my 4th game, 49/49, still no badge. It reports that best so far is 7.
 "Neverending Light"){kind=icon}