Had similar happen to me, received another persons order by accident. I suppose given thenature of most businesses a mistake will occur at some point or other. I received a very expensive table book instead of apin feather holder I was expecting. Simply contacted the seller/store and was asked if I could forward it on to the customer and received a cheque and voucher in the post, along with an apology letter.
Received my parcel a few days later and thought nothing more of it. What was her letter about? Stating a mix up? Did she send you the book along with it? Assuming you ordered online wouldn't there be an email address that you could have been contacted on instead of a letter?
I wouldnt be concerned about my name and address was sent to someone as a genuine mix up, I would be concerned about payment details on the invoice, though I think there is nothing malicious here.
I wouldn't report them to ebay, especially if they apology and rectify things for you. Certainly would mention it in feedback