Don't worry about it.
Tracking is only useful to the seller, since it protects him against false claims of non-receipt.
If 20 days have passed since purchase, use Contact seller to ask for the correct tracking number. If you have done this and were given a number that does not work, RED FLAG!
Go here:
http://resolutioncenter.ebay.ca/
and open an Item Not Recieved claim.
Do NOT allow the seller to offer a replacement. There is no reason to believe the 'replacement' will ever arrive either, and shipping will take you past the deadline for a refund.
Ask for a refund. Only.
Items sent from China often take 30 days to arrive. So a request to wait until Day 30 is reasonable. But no longer.