My brother failed to save before battling the legendary (groudon), and saved afterwards when his team had been wiped out by groudon. Upon returning to the cave of origin, to the same spot that groudon first spawned, he is not there. What can be done to make groudon respawn so he can be battled again, in order to advance in the story?
(Apologies if this has already been answered. I could not find the answer when I searched.)