What I did in the past was assigned an account to an attribute. Then on the clientside, just have a check to see if the player is equal to the attribute. For better reliability though, it may be helpful to use a timeout script in case you plan on changing the attribute to another player. Hope this helps.
PHP Code:
function onCreated() {
this.attr[5] = "Tim_Rocks"; //Your account would go here;
}
//other functions here, just make sure to have the proper checks.
//#CLIENTSIDE
function onCreated() {
if (player.account != this.attr[5]) {
this.hide();
} else {
this.show();
}
}