When you discard cards at the beginning of the game, where do they go? The appearance is that they get shuffled back into the deck. However, after discarding key cards and not receiving them the whole game, I am now wondering if they get put in the bottom of the deck. Where do they go after being discarded?
They get shuffled back into the deck before your cards are drawn again. I've had a case where I put back 2 Ironbark Protectors and got back 1 on the draw.
You not drawing them is just unlucky.
Edit: According to Blizzard, that is not the correct functionality of the Mulligan.