You can ask for the address of the person who should have gotten your book and a credit or postage to cover it, and then send it on to the correct person; they hopefully will do the same and you will both get your books.

For future reference, if you receive a completely wrong book, don't mark it as RWP until you have contacted the sender. You should find out if they mixed up shipments and are willing to help get them to the right person. You don't mark your book until you have actually received the one you ordered. If you never get it, they system marks it lost and you get your credit back. RWP -wrong book is for situations where you get the wrong binding, an ARC or something like the wrong edition.

This is the specific part of the Help Doc listed below:

• ...click on the transaction and send a Personal Message to this sender asking if she sent you this book by mistake.

• If she did,
• and sent your book to another requestor, she can offer each of you credit or postage to send the books to one another; the sender can provide the addresses in Personal Messages.  When each of you get the correct books, you can mark them received.