If the item is very expensive package, the seller should use China Post registered air mail to ship it. But in fact, he uses China Post Ordinary Small Packet Plus which is a cheap service. It couldn't be registered and is easy to be lost on the way. Also, it usually takes two months to reach.

As it's not registered, it couldn't be tracked after it leaves China. No one knows where it is now. If you couldn't receive it within three months, it may be lost on the way. You'd better open an dispute to eBay to ask your money back.