Interesting... I guess in this world RAB didn't get to the locket as I can't see a diviner being mislead in the same way Dumbledore was. I suppose it might be that Slytherin had two lockets and RAB switched them but still...
A good story so far though it does come across as a bit shallow at times I'm afraid - while we don't want to be bogged down in details it seems sometimes things jump out of nowhere, like the unravelling magic bit.