Late last year I had a similar experience with an eBay purchase.  The
seller delivered an item that was damaged, and he then accused me of
causing the damage.  Emails were exchanged and I down-loaded each one
as possible evidence.

EBay expect seller and buyer to resolve differences and seem unable to
resolve issues, although they have the ability to apply short-term
sanctions.  One is therefore rather alone.

I decided that the only course of action was to use the eBay "Feed-back
Forum", coupled with a threat of litigation for breach of contract plus
damages (not an idle threat).  I felt weak because I was dealing with
an agent in New Zealand, whereas I am British.  This approach worked
and I received my refund less the deduction for processing it at my
expense plus the loss of the cost of return postage at my expense.

As the French say. "C'est la vie," but at least it worked.  I suggest
you should pursue your case vigorously.  EBay participants work on
a basis of mutual trust.  If you spread the word by email about a
breach of that trust, then there is a possibility of satisfaction.

Regards,
Paul Bellamy
Kent, England