Interesting story for sure!
About the missing bobbin- I've been selling on eBay for years and am an occasional buyer as well. If it came w/o a bobbin you need to be reimbursed for that. eBay is a buyers market and they do anything and everything to satisfy the buyer.
I wouldn't back down on that one but I just realized you didn't specifically ask about that. Still, I would hold the seller responsible for it.