Noticed "Sparky's Challenge" in the events tab, and had time to kill so decided to play it. Got 2 victories rather easily, and collected a card reward after each. However, after my 3rd victory I was taken directly back to the home screen with no "random cosmetic" reward, and "Sparky's Challenge" completely gone.
I manually checked my cosmetic inventories one by one, and nothing new is present. Tried closing the game and reopening it and repairing the files, still have the same issue.
Feel I was robbed/cheated a bit. Not cool.