This week, I've had 2 battles (1 lose and 1 won) got 11 and 45 rift coins respectively. But when I checked my stash, my rift coins still at 983 (before and after battle. Still same) later I just use for buy something from Cabinet, it can reduced.
I'll check it out. When you restart the game does your stash update? There are a few areas in the game where items won't update until the game is 'refreshed,' one way to do so is to restart.