No AR needed. Remember Giratina Go back to where he was before and youll find an item ball, it should be rare bone. When u get it, exit the cave then enter again and find the place where he was standing. Another 1! Do this as many times as u want. If nothing is there, that means it took u so long to get there. u have a limit of 20(i think) rooms to enter untill u find the spot where he was. If you took more rooms than the limit, u might get something like a nugget or something worth less than a rare bone or nothing at all.
Sell your rare bones for lots of cash!