Hi,
You cannot entirely blame the seller. Either the post must be sitting in customs or must have been lost. The sellers in USA assumes the post everywhere in the world is as efficient as in their country. But many a time, there is theft from the Indian Post Offices. Judging by the feedbacks of the seller, they are genuine sellers with a good feedback.
You should have ensured that the item was send by a service which has end to end tracking. Global priority does not have any kind of tracking.
How did you pay for the item. If you paid by paypal, log into Paypal and you can claim the full money back by opening a disputer. If you paid by credit card, you can call up the credit card company and block the payment.
Cannot do much if you used other methods of payment.
Next time, when you buy internationally ask for a service with tracking. Is a lesson for sellers too. If you accept payment by credit card always send to the verified address with tracking.
Onesimpleman