What reason did you give for the return? If it was a straight change of mind return your seller could have declined it if they were a private seller with 'no returns' on their listings.
You needed to have opened a 'Not as described' return with reason 'does not seem authentic' and your seller would have had to accept the return and send you a return label.
If you paid via Paypal you could try opening a case there, but sign up to 'returns on us' first otherwise you'll have to pay your own postage back.
Note: Sometimes Paypal ask for proof that it is fake.
