If you did everything correct, including tracking through Paypal, then you should contact Paypal. eBay has no control over chargebacks. I would contact the buyer via email or eBay messaging and let them know you will be contacting the following people:
#1. Postal Inspection Service as if they do not return your property they will have committed mail fraud/theft of mail. Let the buyer know they should be expecting a knock on the door in a week or so.
#2. Police both on your end and the city they live in to file a property theft report. Give them the address of their police department. Call the PD on their end and talk to someone about the theft just to obtain a name and rank to pass onto to the thief/buyer.
Give a date when you expect your property returned. Then state you will be following thru on the above items the following day. Set dates and times for your expectations. Keep them short and to the point. Let them know you will not be going away. Above all, follow through and let them know they should be contacted shortly.
I have had this happen to me on a couple of occasions and each time I received my property back. I was fortunate to have a small local PD who sent a certified letter to the thief documenting the transaction and requiring them to return it to me. Each time the buyer contacted me letting me know that they would be returning my property and that they could not believe I would have gone to the lengths that I did to get it back. One item was for $100. Frankly, I would have flown to their city and filed in court as a matter of principle. That's just my opinion. Good luck!
