That is the only way. There are roumors about waiting for the 100th launch in Mossdeep city but they're all fake.
You may use GameShark or Action Replay to get one, though.
You need a mystery gift event, which gives you a pass to go to an island where deoxys is.
simply put: no deoxys is only obtainable in the Firered or Leafgreen but only with a certain ferry pass
Oldsmobile
Birth Island, but you will have needed to get the Pass to get there first which is an expired event.
AUROA
There is no password. In order to get Deoxys, you must pass all bonuses with all playable Pokemon in Rayquazas Balloon Panic.
Olivia, Auroa,and Joanne
You can get the auroa ticket by going to a sponsored Nintendo event, stopping by the Nintendo Center in New York City, New York, or by using action replay cheat code (or Game-shark.)
If you have the Mirage pass you can go and get Deoxys and Jirachi. To get the mirage pass you need to go to a Wonder Spot. No need to thank me [:-)
It is mounted on top and inside the fuel tank.
You get by getting the auroa ticket and going to birth island with a Nintendo Event
The answer is Sleeping Beauty, Auroa or Briar Rose