Hi there, thx for your information and help! Here are some updates:

I've tried a lot with eBay CS team, they won't close my case as usual since they said they do not honor a receipt as a proof of authentic even it is directly from an authorized retailer....

And the buyer today also replied me who said refund me for the fake item without any support such as photos, or something else. Really annoying for this case. I just feel like the buyer has a higher possibility to be a scammer or just kinda change of mind. He cannot provide me anything while I have given him everything needed. But seems eBay still not convinced by myself. 

sorry for the inconvenience 😞