After I beat the Pokemon league , Mr.Medal dissapeared and I dont know why.... if anyone knows why please tell me, I would really appreciate it! Thanks!
He only appears in the Pokémon Center when you have accomplished something in the game. If you talk to him he will give you a Medal, once you leave the Pokémon Center if you go back in he will have disappeared, not appearing again until you have accomplish something else in the game.
Hope I helped :)