When trying to recover a lost account or items in Runescape it may be necessary to not only petition Jagex via their link above or via email but I would also recommend creating a new account if you do not have access to your old one or the password was changed. Once you have a new account complete the in game tutorial in order to get off newbie island and into general population. Travel to a major city on free to play like Varrok or the like and look for a mass of people in order to have a better chance of finding an in game mod.
Here Moddie - Moddie - Mod
Once you have located your Runescape moderator message them and explain the situation these individuals have the ability to restore lost items and accounts depending on how long they have been doing it and their primary purpose is to keep and restore order to Runescape's gaming environment.
I would also recommend adding your main account to your friends list in order to monitor and message the individual who has hacked your account (assuming this is the reason you are here).
Don't Be Foolish
If you are able to make contact with the hacker then tread lightly. What I mean by this is please don't go off freaking out on the guy, this will just fuel the fire they have created and make you look more like a kid, child or a flat out newb. Let's face it, Runescape is just a game, although we take great satisfaction in our levels, quest completions, items gathered, and our online relationship, it's still just a non-tangible reward system that does not apply in the real world and a hacker is only playing a game created by themselves in taking your account. Be courteous and ask nicely for access back to your account to ensure the best possible chance of this guy or girl seeing that he can move on to a new victim and leave you alone since he didn't get the response he or she most likely wanted. Although they may end up taking some or all of your gear you will be that much closer to recovering your account and/or items. Don't get upset, just take action.