Hello, thanks for you response. I am a private seller.

I originally asked him to open a case to say item missing in transit/damaged, but he said that option wasn't available to him at the time so he marked it it as item not received or something similar. 

eBay gave me the the option today to ask them for help, so I explained the situaton (that he received the packaging with the contents no longer inside and the package tampered with). eBay have now asked the buyer to return the item, but obviously there isn't an item from his perspective.