Did you pay?
Did you pay through Paypal or through your credit card?
Guest account claims are a mess-- another question for the Weekly Chat, I guess.
You will have to make your Claim through the payment processor.
But first, remember that many sellers, especially of cheap items, do not use expensive tracking. But that the postal system is very good at its job.
Has it been at least 20 days from payment if the seller is in North America? (forAsia make it 30 days)
If so, call your cc Customer Service at the 1-800 number on the back of the card and ask about a chargeback.
Have the date of purchase, the payment and the currency handy to help the clerk with your refund.
If you paid by Paypal the system is simpler. Come back and ask.