Winner of a GA I created unchecked he received it

yop!
So actually I'm in a pretty weird situation.

5 months ago I created a GA, smone won it, I sent it, he checked he received it, everybody was happy.
Just yesterday he unchecked it, so now I've got a "not received" on my profile.
I added him on steam and asked him why, he deleted me immediately.
Is there smth I can do ?
Can the support be useful ?
Does the report player fonction work now ? (I used some times ago for a guy who didn't activate a gift and...nothing)

• I took a screen of our (short) conversation
• I still have the email with the key I've sent to him
• he has the game on his library (I didn't take any screen and only friends can see his profile but anyway he could have gotten the game elsewhere)

Thanks.