How do you find Mirage Island in Pokemon Emerald?
You can just complete the Pokedex. Talk to the game designer at the hotel in Lilycove. The game designer will give you a small hunt of a Jirachi. After you catch it, you get out of that prison. Go to Pacifidilog Town and go to the bottom right house. You will see an old man. Talk to him. If he says he cannot see Mirage Island, then you leave your game boy on, but have it on charge mode. After 2 hours talk to him again to see if he sees it now. Be persistant; keep doing it. Surely Mirage Island will appear.