[BUG] Not earning Mastery Level 6 token

I played a game as Kog'Maw and a few things happened after.

Upon exiting the victory screen at the end of the game, my client crashed. I opened a new instance of League and upon logging in I was told that first, I had achieved mastery level 5 on Kog'Maw and, second, I had received a level 6 token for an S- rank. I thought nothing of it and played another game.

Upon inspecting my materials, however, I have not found any such token. I have closed an relogged into League and still see none.

I do not know whether the bug is in me not having the token, or with it telling me I had earned one in the first place. I also do not know if the token was not received because my client crashed or because it was earned during the game I hit level 5, or if I was not even intended to earn it.

Any help?