Leglessracing
I should Work at Oakley
I would be very reluctant to accept the return or refund the money. If they don't come back in exactly the same condition with all the same parts, you could be getting scammed. Let eBay or Paypal come after you for not refunding the money, but don't send it until you are 110% satisfied with the glasses.
I had a problem like this too on a unrelated matter. As soon as you receive them back and it's confirmed, eBay/PayPal will give the buyer a refund even if parts are missing and not as you sent them. This is what they call buyer protection. You then have to make a claim against eBay/PayPal and they will want the items sent off to a authorised repair shop to have a quote on what is missing or damaged. It's a really backwards way that they do things and leaves the seller right out of pocket!