S- Rating No Mastery Token

Hello!

I have mastery level 5 on Blitzcrank, and received an S- in my last game with him going 1/2/20. However, I did not receive any mastery token. Why might this be the case?

Thanks

Edit: Relogging presented me with the token, though it was not there after the game. It appears as though other people are having this same issue as well.