Unfortunately, some times there is nothing you can do, other than as one comment suggested, taking pictures of the item with all internal packing visible, prior to closing the exterior box. As the seller, unless otherwise provided in your ad, you are responsible for getting the item safely to the buyer. That is why you should always insure whatever you are shipping. At least make the claim for the $100 if you didn't insure it!
That being said, the story does sound fishy, as the factory internal packaging should prevent any damage and the likelihood that there was damage to the internal packing without any exterior damage is pretty slim (but not impossible, I suppose). You clearly went above and beyond the call of duty in trying to make the buyer happy.
Compare that to an experience that I had on here buying a $2K subwoofer. It was packed at a UPS store. When I received the box, it looked like some UPS employees used it like a soccer ball. The exterior box was significantly damaged, the interior box was also damaged at the same places, corners were crushed, knobs broken off, etc. I took pictures of everything before I opened the box and then documented everything as I opened it up and showed the enormous damage. I called UPS and they said it was only insured for $100, but that if it was packed at a UPS store, the UPS store would refund the purchase price, BUT ONLY TO THE SELLER. I told the seller that I was sending it back to him to deal with. Seller refused to refund my money, claimed that the shipping damage was my problem, and when I opened a PayPal dispute, argued against PayPal paying me. Although PayPal initially ruled against me notwithstanding the photographic evidence, I called PayPal and complained and they ultimately ruled in my favor.
So, the moral of the story is that stuff happens. Sometimes outside of the control of either party. But if you take steps to (1) document the packing, (2) insure it, and (3) as a buyer, if the box looks damaged when you receive it, start documenting the unboxing, you can avoid most problems with people who have good feedback.
That being said, the story does sound fishy, as the factory internal packaging should prevent any damage and the likelihood that there was damage to the internal packing without any exterior damage is pretty slim (but not impossible, I suppose). You clearly went above and beyond the call of duty in trying to make the buyer happy.
Compare that to an experience that I had on here buying a $2K subwoofer. It was packed at a UPS store. When I received the box, it looked like some UPS employees used it like a soccer ball. The exterior box was significantly damaged, the interior box was also damaged at the same places, corners were crushed, knobs broken off, etc. I took pictures of everything before I opened the box and then documented everything as I opened it up and showed the enormous damage. I called UPS and they said it was only insured for $100, but that if it was packed at a UPS store, the UPS store would refund the purchase price, BUT ONLY TO THE SELLER. I told the seller that I was sending it back to him to deal with. Seller refused to refund my money, claimed that the shipping damage was my problem, and when I opened a PayPal dispute, argued against PayPal paying me. Although PayPal initially ruled against me notwithstanding the photographic evidence, I called PayPal and complained and they ultimately ruled in my favor.
So, the moral of the story is that stuff happens. Sometimes outside of the control of either party. But if you take steps to (1) document the packing, (2) insure it, and (3) as a buyer, if the box looks damaged when you receive it, start documenting the unboxing, you can avoid most problems with people who have good feedback.