Mastery Token help please

I just finished a game of Hexakill with an S-, but did not receive my mastery token. I was playing Soraka and i am at mastery level 5. I was looking through the forums but most of the discussions on this are almost a month old. I already have 1 token, this would have been my 2nd. I saw it suggested elsewhere that you can only get the mastery tokens on Summoner's Rift. I don't recall where i got the first one and am wondering if it is a bug or lag or something or if you can only receive the tokens on Summoner's Rift.