If Hetian jade tag is lost after purchase, you can contact the seller and ask if you can return it. If the seller agrees to return the goods, you can return the goods according to the seller's request. If the seller does not agree to return the goods, or can't contact the seller, you can apply for the after-sales service of the platform. When applying for after-sales service, you can explain the problem of the goods and the loss of the tag in the "Problem Description". The platform will review according to the specific situation and provide returns or other solutions.

This is just a general suggestion. Please choose the appropriate solution according to the actual situation, and consult a professional lawyer for legal advice if necessary.