I think this is a difficult one, and I agree that it is not an issue for RISI admin to sort out, as the other swapper has entirely fulfilled their part of the deal by sending you the book you requested. Really I have to say that it was up to you to make sure you knew what you were swapping for. No one is forced to swap - presumably you chose this book off the other swapper's list in response to a request from them? What categories was the book listed under? Even if there wasn't much information given under the book description, it is possible to research titles on Amazon etc, and to be honest, unless I'm absolutely sure a particular book is definitely what I want, I don't agree the swap.
As for your comment that "this lady hasn't had her star rating changed", I'm not sure I understand this - do you mean you left her 5* because there wasn't a suitable option under the list of reasons to leave less than 5*? In cases where you are unhappy because you feel you've not got the book you expected, you should really email the other person straight away to explain the situation, thus giving them the chance to offer to swap back, or to offer you another book off their list that might be more acceptable. Then you should only leave feedback once you've given the other swapper the chance to remedy the problem.