I'm terribly sorry for the delay in my reply Ruchpakorn, & for any confusion! We can't actually review any account information (transactions) through here due to privacy & security concerns. I do want to make sure that we address this issue, so I'll be sending my reply in two messages to ensure that all the links come through okay in Facebook. Sorry for the extra message (or notification) in advance.
It sounds like you've done everything that you can to take care of your buyer in this type of situation. However, please keep in mind that Defects are only removed if it meets our criteria under certain circumstances. To see what's qualified for the Defect Removal Policy: http://bit.ly/XYU3Qm
In this type of situation, it doesn't sound like it would meet our criteria for removal. Do keep in mind that this mark on your account isn't a reflection on your reputation as a seller, but a way that we keep track of our buyer's experience. If you do feel that your buyer might be abusing the transaction, you can report them to us so we can review the account to see if there's anything that might qualify for the feedback to be removed. You can report them through the Seller Center here: http://ebay.to/1EHWxtq