Mt. Stark.
He lives north of the Battle Frontier.
in the battle tower in the not with a friend multi battle room (by yourself)
Buck is on the battle frontier after you battle Volker and a person from the elite four. But you can only go to the battle frontier after you have beaten the elite four and after you have seen every Pokemon in your pokedex. Once you have go show your pokedex to professor Rowan. Then go to Snowpoint citie and go to the boat just in front of the town. The the sailor will take you straight to the battle frontier.
there is a club in the survival area and you can battle gym leaders there but also people like Riley and sometimes buck appears for a battle.
Battle of Buck Head Creek happened on 1864-11-28.
Francois & Perrault discovers that spitz is missing and the signs of battle on buck's body are the proof that the inevitable battle between buck and spitz has occured and that buck is the winner.
Battle Tower.
First, you have to go to the Multi Battle room and have 2 eligible Pokemon participate. If you've helped Buck before, then he will appear in the Battle Salon. Press 'A' on him, then answer 'Yes' to all of his questions. You will battle alongside Buck. He will only attack the opponents, giving you a perfect chance to inflict heavy damage on his Pokemon.
After you speak with Buck and he says he will put the Magma Stone back, you will next see him in the Battle Tower. If you select the Multi Battle option, Buck will be one of the trainers you can team up with.
the survival area battle cafe BUCK
he is in the top left house in the survival area ,talk to him then you can go and catch heatran at lv.70 ( first you have to help him get the magma stone in stark mountain!) the best ball to use is a dusk ball (get its health down first!)
He's another partner in the battle tower multi battle