Return from Bass & Associates

I sent a C&D letter about a month ago to Bass & Associates. I sent it certified mail, return receipt requested. I never received anything back. In Saturday's mail, I got a certified receipt and where they have to indicated who the sender is, it was marked "return." I have not been able to pick it up yet so do not know who it is from. I am wondering if Bass has just returned this to me without signing for it and that is what the "return" means on the receipt I have gotten. Has anyone had anything like this happen before?? I am not sure what to expect when I go to the post office to pick it up and thought someone else might have had the same experience. Thanks.