I don't understand why people on this site are always so unwilling to believe anything without thinking there is some conspiracy theory behind it. :shrug:
Sounds perfectly plausible to me. I have bought movies at resale shops before and I must admit, I don't think I always open the case and make sure the right movie is there. People don't always do that which you think is the "obvious" thing to do. And as for "why not use banks"....I have stashed money away in the house, too. Not in a DVD case, but in a more secure place in the house, like the little safe next to our bed. I don't save it up in a bank. When I am saving for vacation funds, I stash the money in my safe in either a zip up bank bag or my special wallet that I only use on vacation. To me, it's too much of a hassle to take it down to the bank, just to go back to get the money out, when I can have it right there in the house ready to grab when it's time. Of course, this is just the spending money portion of it, since I have always payed for the bookings and the tickets with our tax refund, in the form of a check written and mailed to WDW.
But the point is, to me, the whole story is conceivable: stashing the money somewhere in the house (although I wouldn't recommend a DVD case), not checking the DVD before you sell it and not checking the DVD before you buy it. Obviously, I'm not saying that the best decisions were made here by the woman, but I can totally see how it could happen.