for future reference, contact the seller first if you have any questions/problems at all., that is how most problems are worked out and ebay says this when you open a return request..."have you contacted the seller?" Maybe you did, doesn't sound like it.
You have now committed to return the machine, ebay did exactly as you requested.
take your own photos before you return it, and how you packed it. They might blame damage on you... Also save photos from their listing for comparison if there are problems.
The seller maybe sold the bobbin case separately, they can make a lot of money that way. Sorry for your disappointment.