It is quite unlikely or impossible they can stop a chargeback because it makes no difference if that place is on your side. All that really matters is if the buyer used a credit card or a credit card via PayPal and orders a chargeback in all likelihood you will lose, regardless of what 2checkout says as i'm sure they have no control.
Even if you can prove buyer purchased it and the domain is now under their whois info you can still lose the case, That's especially if buyer lies by saying charge was unauthorized then it becomes a more or less automatic loss for you.
To make it worse, the credit card bank or paypal will NOT make the buyer return it. In fact, they won't even ask them to do that by saying it's against their policy.
P.S. Years ago I lost 1k on a purchase with the credit card charge back first started by buyer 13-mos after the product delivery date. That's NOT a misprint it was 13-months later. I battled it hard but the bank did not care and refunded the money. That buyer was not required to send back the more than 1 year old product!