Ebay has the easiest system in the world for buyers to force sellers to
take returns. Just open a case for not being sent the right product,
send it back at sellers expense and get a full refund..
If tracking shows delivered its very unlikely you will loose a case if
they opened it for no arrival. Ebay is usually pretty good about that.
Now, if they opened a defective case that's a different story but at
least buyer would need to send it back.