I'd say wait it out and see if the seller contacts you. If he doesn't, you're not legally required to return it. He probably will end up noticing though after some poor sap who bought a tv complains about receiving headphones.
He sure comes across like an unscrupulous scammer.
Most states in the U.S. have a
statute that protects the receiver of unsolicited products from returning them. I am not sure if a mistaken order counts as "unsolicited," but I bet you could make a pretty damn good case that it is. Don't send the wrong merchandise.