[CLIENT] No Chest for S Rank on Champ I Don't Own

I queued up for a game of One For All (the current featured game mode) and played as Gnar (who i do not own at this time) due to the lottery system. At the end of the game I was awarded an S rank but no chest was given, even though it was announced you could earn chests in the rotating game modes. To Replicate Step 1: Queue up for One For All. Step 2: Have the champ chosen for your team to play be one that you don't own. Step 3: Acquire S+,S,S- through whatever means possible. Step 4: Reach end of game lobby.