I don't really know about something like user or loss protection here on Amibay. It is really your responsibility and risk when you buy something described as "NOS". "NOS" usually means "sealed", "not opened", "not used". You take the risk when it will not work. When seller sells something as sealed or NOS, and it is stated as this, this is really your responsibility in case it will not work. Otherwise you can ask seller to open it and test it, but I don't think that somebody selling thousands of disks will want or will be able to test every disk he sells if buyer will ask for it. Normally said, don't buy anything if you don't want to take a risk that something sold as NOS or "sealed" or "something similar" will not work at the end.