If the item you purchased doesn't turn up by eBay's latest estimated date of delivery then open an eBay Item Not Received case against the seller. In order to win a case against you the seller would need to prove beyond all reasonable doubt that delivery to the address that you had provided at Checkout had either been attempted or had been succesfully carried out. If, however, the tracking showed delivery to an address other than the one that you gave to the seller at Checkout when you paid for the item then eBay ought to decide the case in your favour and refund your money in full.
If you do end up opening an Item Not Received case on eBay but for some reason they decide the matter in the seller's favour then there are alternative ways with which to pursue a refund. If you paid for the item via PayPal then open a non-receipt case on PayPal if the eBay case is decided against you. PayPal tend to look at cases far more closely than eBay do, so once they've examined the tracking and have found that the item was not delivered to the address that you provided you will more than likely receive a full refund. However, if you do find yourself in a scenario where eBay fail you and close the case in the seller's favour and you subsequently choose to open a PayPal case, make sure that you escalate the case before PayPal's twenty day cut-off period should it become necessary to escalate the matter in order to achieve a full refund.
In the event that you paid for the item via credit or debit card then should the goods fail to arrive the best option would be to start a chargeback. You have one hundred and twenty days from the date of payment during which to do this if you paid using this method, so you ought to be able to secure a total refund of the money that you paid to the seller.
