I use Ebay on a regular basis to look for and sometimes purchase antequarian books. This is difficult because the buyer faces the same potential problems as stamp collectors do.
That said, I have never had a bad experience on Ebay. The product was always as advertised; seller responded to specific questions I would have about the book (is there a partial flaw on the first word of line 4, page 43....); I usually pay by money order and books have always been wrapped wonderfully.
We are not talking your regular bookstore values here either: I have bought books on Ebay in the 5 figure range (although as the price goes up, I begin to request digitial pictures of known flaws in a book).
For ANYONE who buys and sells on Ebay, they have a rating system. You can click on the name of the person and it will bring up any negative ratings they have received. In addition, you can see the comments that were provided. I usually only deal with sellers who have bookstores and have more than 500 transactions. But I have also bot books from people just starting out (20 or 40 sales) and have been pleased. You have to decide what "limit" you are comfortable with. I think that if you ask questions to the seller about the product, you can sometimes get a feel also for how the transaction will work out (that is pure specualtion on my part--although I have developed good book contacts thru these emails on Ebay).
How much money was involved in the purchase of the bra, if I may ask? And was the person selling more than one?
As one of the posters said CAVEAT EMPTOR!
Hope all is well now