Mastery Tocens Error!

I played Corki at U.R.F. mode and i've got a S+(btw. I am level 5 at him) and i didnt get my mastery level 6 tocen,so I think it was a bug.Now I am not sure if it is possible to get a mastery tocen in the Ultra Rapid Fire so if somebody does i would appreciate him/her to tell me in the comments about that.