How to black list the IMEI or check the activation status of my lost iphone 4S?

I sold my Iphone and shipped it out of the country. I had a US tracking number, but when it left the country i'm told that it didn't have a tracking number. The buyer says he has not received the phone yet. I sent it to Bulgaria. Is there a way to track the package using the US tracking number? Or can I check the activation status of the IMEI? Can Apple do anything?

Nope, once it leaves the US without a tracking number, it is fair game, and the buyer can claim he never got it and demand their money back. You may have some recourse if you got insurance on the package through FedEx, UPS or DHL.

You can always report the phone stolen if you can't track the phone. Just don't tell them that you sold it, say that it got stolen on a bus or mall or something like that. If you're the original owner of the phone, it won't be a problem. But unfortunately, blacklisted phones pose no problem when used outside the country.