@Penelope89 OfferUp would take the loss. We investigate each and every chargeback we receive, and OfferUp takes the loss. If a seller sends an item, and the buyer does a chargeback, we would not even be able to take the funds back from the seller, so we eat the costs. This is another thing that shows that there is seller protection built into the flow.
If a third party app was used, you would be subject to their terms @Bricio. As no funds were processed using OfferUp, we wouldn't be able to provide this sort of refund.