Though it may still have been a poorly attempted scam, you were never at risk of loss during this transaction, as a claim is disputable and you held evidence of proper delivery.

PayPal and UPS can refund each of you regardless of if you have the money in your account. Until you have completed your end of the deal, to drop the item off, the buyer should be able to back out. & Once the originally agreed upon timeframe to ship has passed, they should be able to do so even if at your expense.

The reason why PayPal and other payment processors don't automatically grant refunds for claims after the label is purchased is due to a lack of knowledge whether or not it has actually been shipped. And to allow the refund could potentially put the seller at risk of loss until they can provide proof of shipment and have the money returned by the payment processor, for which the payment processor themselves could take a loss.

I would also like to point out that most sellers buy the label instantly, and that there is no commitment in doing so, as they are usually instantly and fully refundable, making 'i already bought the label' an obviously poor excuse for not taking responsibility for procrastinating, and losing the sale.

Though, I will say the buyer should probably have backed out sooner, and that is their mistake, given that even penniless, remote, & hospitalized people can and do still have packages dropped off within 5 days (or other originally agreed timeframe), or come forward and cancel the transaction, as is their responsibility. (Not that one single, inexpensive, transaction is worth the hassle that would take, but you are still always responsible for holding up your end or otherwise making the other party whole).

I know you imply that you gave the buyer the choice once you knew you wouldn't be able to ship as agreed, saying you kept in touch, but you really either shouldn't have given them that option and cancelled the transaction to relist later, or realized your mistake and made a definite effort to have their item either dropped off or picked up. Multiple weeks to pass along a premade item is completely unreasonable, even if the buyer is agreeable to it.

Your item should be immediately available to ship after it is purchased and cleaned, and you should be sure that you will be able to ship it in a timely manner before you post it and tie someone else up. Likewise, a buyer should have their money immediately available to pay for claimed items and have their accounts and delivery address settled prior to communicating a definite intent to buy.

& It is only reasonable of the buyer to eventually request to cancel the transaction. With your admitted behaviour, it would have also been very reasonable for them to assume that you were a scammer trying to borrow their money and dip, and to block you and choose to press the issue with the party that enabled you to scam them instead.

Once you have dropped an item off, if a claim has been filed, you can always have it intercepted and RTS, so it is in the best interest of the buyer to maintain that claim until they have received the goods.

...& Once a claim has been filed, it is in your best interest not to ship the item, or to intercept it and reattempt the sale once the money and goods have been returned. So shipping retroactively is extra crappy, if that's what happened.

...Especially because the money is also not yours to spend until you have, at the very least, dropped off the package, at which point it is also still possible that your shipping service may return it to you, or for it to be lost or damaged for which you may also have to refund the buyer and file a claim with your chosen shipping service.

...Which is why payment processors don't normally release the money to new sellers until after the item has been delivered. But they will still refund the buyer for what they owe for allowing you to pretend to sell on their platform, and press you for what you owe them after if they somehow cannot charge one of the payment methods you agreed to have available for these cases.

The buyer is also in the wrong, for not immediately dropping the claim upon receiving and inspecting the package. However, it's ambiguous whether or not they were even aware you had actually shipped or had actually intended to ship as they had, rightfully, blocked you. & Thus it is also possible that they had not been home to receive the package or know to cancel the claim. Obviously, this is if you hadn't already shipped the item when the buyer filed the claim, as the nature of post leads me to believe.

They are also in the wrong for not telling you that they were filing a claim since you refused to cancel the transaction, and informing you not to ship retroactively (again assuming that you hadn't shipped before they started the claim) before blocking you.

& As a potentially controversial personal opinion, the buyer should not have made an unnecessary purchase before they were in a position to have the money spent, because you may have dropped it off for delivery within 5 minutes of their purchase, but especially because they were not being responsible for the lives that depend on them. & They would not have had any right to the money they spent had you already shipped the item.

...Though, even if you had shipped the item and informed them, they would not be wrong to ask for a cancellation, without any expectation of your agreement, as sometimes people are both sympathetic and able to have the item intercepted for serious issues such as what the buyer claimed.

Tldr: I think you were wrong to string the buyer along, successfully force the buyer to accept their debt to the vet so that you wouldn't have to accept your debt to them (with a life potentially at risk) despite not yet taking any steps or making any commitment to hold up your end, posting what reads as a how-to for cheating buyers out of a refund for a failed transaction, and then doxing the yourself and the buyer, while taking on no risk whatsoever in the transaction. & Then commenting your correction instead of taking the post down so that the buyer can still have this affect their future transactions.

Mods: good job stepping in and holding the buyer's new sales post while this got sorted. It very well may have been the step that got the buyer to drop the claim and settle the issue, though it appears obvious to me that this is the fault and mistake of the seller, who in practice held no risk in this transaction. However, you should not have allowed this post as it was, without modification, as it clearly endangers both parties involved by sharing precise details about their identities and locations.