I've never gotten a bootleg personally, but my brother once got a bootleg dvd via Amazon (it was a birthday gift for me, so he had me help him with the return.)
The most important thing is not to waste time. Only give the seller 2-3 days or so to write back before you contact him again. If you don't have a good solution within a week, be ready and willing to open a dispute.
Most bootleggers are quick to issue refunds, since they usually still get postitive feedback that way, so they look better to future buyers. The nastier ones will come up with excuses to waste time so the dispute window passes- don't allow that. Pick a day you will file a dispute by if it's not 100% settled, regardless of what's going on in your communication. Write it down, and stick to it- you can always close it later when you get your refund.