2CheckOut is just an independent online payment processor, similar to PayPal; these services act as a middleman between you and the merchant, so when you checkout, you are actually paying the processor, and then the processor then pays the merchant.
I can't say for certain, but I might speculate that to maintain good PR and buyer confidence, 2CheckOut might simply be "reversing the charges" unilaterally on their own upon complaint, with or without the merchant's cooperation, and if so, they may be using their own methods to get those refunded funds back from the merchant in turn.
Also, many thanks to Marie for filling in some details to help others here. :^)