If you are able to contact the seller, then you are probably able to study the Ebay auction listing. If you know what was stated in the auction, then you are in a better position to discuss the situation with the seller.
If you need to make an insurance claim due to the bobbin winder breakage, be sure to keep the packaging materials in case the shipping company wants to examine them to determine whether or not the machine was adequately packaged before they pay the claim.
Good luck with this. I am sorry this happened to you.