Does the order of the discard pile matter? I was watching some 2013 world footage and I noticed a player kept all their pokemon at the bottom of the discard and did not keep the cards in the order they went to the discard pile in.
No. It doesn't matter. Some players will put pk or mom or energy at the bottom or top so they are easier to find based on other game effects. You do have to be careful though in organizing your discard pile that you don't take too much time and be called for slow play but sorting and searching multiple times for no real reason