Walkthrough
After losing out on the Sapphire in the Dotted Hole, head to the Rocket Warehouse on Five Island within Five Isle Meadow. Now having both passwords, you can enter the building in hopes of getting back the Sapphire. Much like the Rocket Hideout, you will need to maneuver through the Rocket Warehouse using moving tiles. Defeat the same Scientist who took the Sapphire to obtain it. Once you have, head back to One Island and give Celio the Sapphire. With it, he'll finally be able to complete his machine, officially allowing you to Trade with those playing Pokemon Emerald. With Team Rocket finally defeated once and for all, the Post Game Story may appear over. But that is far from the truth.
Pokemon Trainers
Team Rocket Grunt: Level 49 Houndour, Level 49 Houndour
Team Rocket Grunt: Level 48 Machop, Level 48 Machop, Level 48 Machoke
Team Rocket Grunt: Level 49 Hypno, Level 49 Hypno
Team Rocket Admin: Level 52 Muk, Level 53 Arbok, Level 54 Vileplume
Team Rocket Admin: Level 53 Golbat, Level 54 Weezing, Level 55 Houndoom
Scientist Gideon: Level 46 Voltorb, Level 46 Electrode, Level 46 Magnemite, Level 46 Magenton, Level 46 Porygon
Items
Sapphire: Defeat Scientist Gideon