okay, follow these instructions if you are in hoenn, pokemon ruby, emerald and sapphire 1- defeat the elite 4 (if you have not already) 2- take one pokemon out of your team, you will have 5 or less 3- fly to mossdeep city 4- you should be in the front of the door of a pokemon center 5- slowly take 3 steps to the right 6- take 6 steps to the north 7- take 12 steps to the left 8- Go inside 9- Take 3steps to the right 10- take 2 steps up and read the message 11- take 3 steps to the right 12- 1 step up 13- press "A" 14- your friend, Steven Stone, left you a very pleasant surprise....
I knew even before I got the Emerald guidebook. When I played Sapphire, and then Emerald(I never beat the Elite 4 with Ruby. Don't ask why I had both Ruby and Sapphire) I knew he left a beldum in his house. Or rather, I knew because when I played Sapphire I wanted to see if you could talk to Steven in his house, so I went there, and found the Beldum. I didn't need the guide to tell me when I got Emerald, but it certainly helps when you don't know what you need to do to catch Groudon and Kyogre, and I suppose Latias/Latios, as well as the Battle Frontier. Either way, I found out by luck, but after I beat the Elite 4 the first time I found it and that's how I knew.