Finally. today pokemon.com realased an article that tell about oaks letter. itll be out from september 28 to november 8. when you get it head to where that fat guy was standing near the end of victory road. head to the end of the route(224) and walk around. oak will appear. he tells you something. you write somethin(anything)then a path(flower meadow)appears you see shaymin and it runs away. chase down the path(a pretty long one)and finaly you meet up with it. i suggest you use a pinir from the mass outbreak with false swipe(bought at the veilstone apartment store)then put it to sleep.stock up with ultra balls.good luck!
this shaymin can change into sky form with the gradicea obtained from the blonde in floroma town with the shaymin in hand.
the word you wrote on the rock will forever
the path, like Newmoon island, you can always revisit it. (its also a good place to hatch eggs)