... Basically what happened here is that you sent a payment directly to the scammer. Coinpayments doesn't actually control the keys here.
Basically if I had not been misleaded by the coinpayments.net payment gate (and as an ordinary person I had the right to think that the participation of a third party is primarily necessary to protect the transaction from fraud and not just for technical convenience of shop's employees) I would have never bought anything directly from those damn scammers
Ignorance of what coinpayments does does not make them complicit. They are just the middle man. It's like blaming the ATM when if you were mugged on the street.