If I was in Barnes & Noble and bought a book, then was approached by an employee saying "We weren't actually allowed to sell you that copy of the book, here's your money back," I might be disappointed at not having the book, but Barnes & Noble retains the right to take that book back from me if they're also returning my money.
That argument would make more sense if Barnes & Noble owned my computer, or if I were still physically present on their store's property.