I think RAB's "I'll be dead before you read this" reference is about the fact that RAB knew that the poison would have killed him long before Voldy ever read the note. Nothing to do with anyone else killing him.

How did RAB find out...hmmm??? Dunno. MAYBE RAB overheard Voldy doing a horcrux creation spell and put two and teo togther. MAybe they got really drunk together one night and Voldy tolsd him/her all about it. MAYBE RAB and Voldy were lovers and V did a bit of pillow talk... now I'm being silly aren't I? So you question is an excellent one and I can't wait to hear others' theories and we'll try and figure it out together.

How did RAB find out where the horcrux was AND exactly what it was???? That's a real stumper. Gotta admit I never thought of this at all.
I reckon RAB knew it was a locket because the alternative -drinking the poison, discovering that the horcrux is a locket, escaping the infera, getting out of the cave, finding the nearest cheap jewelry shop, buying a locket, THEN, poisoned and stumbling through that cave and all it's trials again JUST to put a fake locket in the basin- is too silly! Naa. RAB MUST have known that THAT horcrux was the locket and come prepared with the fake and the note.
You are so right 100%, how did RAB get so much info??


Great points you've raised. Ta