If no tracking number was shown it was probably sent without tracking. Sellers can send items without tracking to save money but if buyer does not receive item (and there's no proof of delivery) they can request a refund through eBay. It's unfortunate that it was over 4 months ago you placed order as that is too late to deal with it through eBay. What was the estimated delivery date? You have 30 days from estimated delivery date to open a case/request a refund with eBay.
As ypdc has said the reason he would have said contact him through orders page is he can no longer see it on his end. If you used Paypal they allow up to 180 days to open a case/request refund but eBay's is 30 days from estimated delivery.