VERY interesting pokemon platinum help needed!?

ok, so i was playing platinum, and i fainted legendary; uxie and azelf. few days later, they reappeared in their caves! so can any1 explain what happened. also i fainted heatran and i tried looking back a few days later but he wasnt there. then i decided to battle the pokemon league. after i beat them, i wanted to c if he was there, and she was!!! ( same thing happened to me with dialga and cressellia) what happened? plzz some1 tell me :)