I had the 15% loot buff from a premium chest, and i logged in and out of the game to clear my browser's cache. When I logged back in, the loot buff was gone, and instead I had the XP buff! Not a visual mistake on my part. Big difference between seeing the yellow/orange "dice" on your bar, and yellow/orange big "XP" letters! It still had the correct amount of time left on the buff as well.
