Take picture of the empty package. Contact the seller. If the item was insured they will contact the post office. If no luck there contact the site you purchased on. You can also contact your pmt provider whether it is a credit card or pay pal. If the seller has been selling for a long time and has good ratings it's difficult to believe they would do such a thing intentionally. However, I have had several questionable incidents with USPS. It's a shame these things happen but it is not ALWAYS the seller to blame. None the less, buyers have plenty of options to retrieve their money. Good luck to you.