Sorry to say but when getting the firey drum, it's Heatran. I think you get it by going to the giant volcano with the secretslab.
How Do You Get Moltres In Pokemon Mystery Dungeon Explorers Of Sky?
After beating the game, side story, etc. And saving Scizor from Blizzard Island, you will get the the secret rank and secret/special missions. When you get the mission to Giant Volcano, accept it and go there. You will come across Moltres and will need to battle it. After you beat Moltres you will get the fire drum and Moltres will ask to join your team.