User verified receiving gift, didn't activate it (profile is now private); won't communicate, help?

To summarize what happened, the user received the gift (I sent it via Steam Gift E-Mail method) and marked it received. I attempted to check to make sure it was activated and it wasn't so I added them to my friends. When contacted they told me "Please don't kidd yourself cyber police" - "I verified gift received, look at my gift inventory" and then removed me from their friends list before I had a chance to respond. Their profile is now private and they won't accept my friend request on Steam.

Important to note: The game is not in my Steam Inventory (normally it would be there until redeemed, saying "gifted to: name@email.com") AND it's not activated on his account (meaning it was moved to a side account, or sold, as far as I can tell, correct me if I'm wrong).

What is the next course of action to take, can a moderator of SteamGifts attempt to contact them or something?

Let me know any other necessary information and I'll attempt to provide it.

Link to SteamGifts giveaway
Link to users SteamGifts profile
Link to users Steam profile
Link to conversation, proof that game wasn't activated, etc