Serebii said your game generates a number every day for each of your Pokemon (it changes if you put it in a PC Box) and if it matches, the man in Pacifidlog Town will say the island's there that day. You can get Wynauts rangin' from level 5 to level 50 and there is a berry patch there with a Leichi Berry.
Siggy proudly brought to you by .Impact!
[insert random quote or phrase that makes the sig space look less bare]