glad to avoid helping!
i wouldn't be surprised if a single dead pixel occasionally shows up in anything that has a million pixels, be it an e-reader, monitor, camera sensor, etc. the only way to avoid it is to have production screening for every panel, checking every pixel, and that isn't going to result in an affordable final product (not just due to the effort to screen, but also due to "so, what do we do with the rejected ones that cost us money to manufacture but have a dead pixel?")
if you ask for exchange, they might ask why, and if you say dead pixel, they may say that's not a good enough reason or give you a hard time. it might be easier and less hassle to just to an outright refund, and then buy another one. but that really depends on the store.