Events no longer are going for Gen III games.
So in order to get Deoxys you have to trade for it. And since I'm doubting any friends you have will have a Deoxys still on their Gen III games and not transferred over to their Gen IV/V games, you're out of luck. Unless you want to hack for it.
You could have recieved the Aurora Ticket (not the Aura ticket) through the Pokemon Rocks America Tour: http://bulbapedia.bulbagarden.net/wiki/Pok%C3%A9mon_Rocks_America
But that has long since passed.