I was just reading OotP and as they were cleaning out the Black house, JKR listed a bunch of different old relics that they were throwing away, and in the list is "a heavy locket that no one could open." It seems kind of throw-away, it's one short line, but it comes right after mention of Regulus, what do you think? Could it be Slytheran's locket? I'm sure this has already been posed somewhere else, but what if it is? RAB said it was destroyed...just wondering if maybe this will be the Horcrux that Harry stumbles upon, in 12 Grimmauld Place, accidentally. If it's already no longer a Horcrux it would make sense for him to be able to find it accidentally. Anyway, I just thought it was interesting.