If you're saying that a buyer returned the item after having damaged it, removing parts or even swapping it for a different one, join the club.
One seller told us that this is how eBay replied: "As we didn't see the original item that you sent to the buyer and we didn't we see the item the buyer returned to you, we are not in a position to take sides in these situations and verify who has the valid complaint". By "not taking sides", eBay of course means that they will take the buyer's side.
EBay has become an absurdly risky place to sell anything of value. The money back guarantee is almost a DIY kit to defraud sellers, with eBay enforcing refunds even when they admit they don't know who's telling the truth.
You can try appealing their decision, if they will accept an appeal, and you can report the buyer, not that this will make any difference.
EBay is unregulated - which is a disgrace - so sellers have no right to any independent appeal. And you have agreed in the user agreement to accept their decisions.
