u/Very_Sexy

I have Allthemons and Mega showdown installed and have been trying to get groudon for a little while now, ive been using pokenav to see if he spawns where i am at, but for some reason when i check it says he spawns and then i check right after in the exact same spot and he has dissapeared from the spawn list. Does anyone know why? Or how I can find him more easily.