Has Anyone Else Had This Happen To Them?

That's actually a misinterpretation of the rule. It's really that a thick or inflexible mail piece cannot be first class mail. It must be first class package. The rule is there to keep thick stuff out of the mail sorters, not to get customers to pay more for thin packages. Some postal clerks mistakenly assume that means that thin packages have to be priority but that is wrong. They can go as either first class letter or package depending on the orientation of the address to the long edge. I have our local postmaster's word on this.

You don't have to pay postage due, but you also won't get the package. They'll send it back. It's double the cost for them, but that's how they enforce it. What I don't get is that for something as light as a coin, media mail is actual more expensive than first class. Was this on line or ebay postage or metered at a post office counter?

To clarify some of the questions that have been asked, the dime came in a business letter flat envelope. It was preprinted and stated that it was postage paid by Pitney Bowes with the ebay logo above it. Below that it said USPS Media Mail. It also had a barcode that said USPS Signature tracking above it.

I have sent two messages to the seller and he has yet to respond. I am going to give him a couple more days, and if he hasn't responded by then I will leave negative feedback. I don't know if I have any other recourse.