Bought PSN 100$ CODE unusable after 2 hours

So I bought a 100$ psn code from a fairly old and trusted seller over here. I verified if the code was f9 which it was at the time when I got it. fast forward to 2 hours when I actually try to redeem it, it said code already used. Of course I had already rated the seller in between and completed the transaction. Now I cant even message the seller to resolve the issue. Iam sure it must have been a mistake as I doubt such an old member to deliberately do it. Now I have sent in a ticket but going by previous records its pretty much useless. So now Iam pretty much in wait and see scenario. If I dont get a response from gameflip, I will have to file in a paypal dispute for this as I dont see any other option.
My code is 8TDBQ5 if any mod wants to fast track this process or at-least get me in contact with the seller

@Tali @DunnBiscuit. Guys help buyer