I don't know if you mean that R.A.B. stands for a group or what. . .
I remember someone else asking that question, but the answer is no (in my opinion, anyway). In the note that was left the person uses "I" and "me." That signifies singularity (I think that's the right word. . .lol). But I do think that another person/creature accompanied R.A.B. to get the horcrux. I don't know about apparating there. . .you'd think Voldemort, being as smart and powerful as he claims, would have thought of that.