Well, much like I said to Dragonnite, the Lock-Heart Guild doesn't disperse knowledge of the Locked-Hearts freely to just strangers, and they aren't labeled as Treasure Hunters. They are honestly fighters, traders, merchants. They appear like a fairly simple guild, to everyone, and no one really knows about the Locked-Hearts other than the Guild. 

You are still more than happy to join them, as most players will likely join them at some point, since they are the general Catalyst for the Rp. It will just be that you are less informed, and won't know of the Locked-Hearts until you make relations with the Members.