To be honest with you, it sounds to me as though the seller has experienced a case of post-sale regret given the low price that you won the item for and now doesn't want to post it. If that is indeed the case then he or she should just own up, apologise for not honouring the sale and refund your money in full. However, I think you're right in that the seller is just waiting for you to open an Item Not As Described case so that he or she can refund your money.
If by the time you read this reply the tracking still hasn't updated to show any movement of the parcel then open an eBay Item Not Received case. If the item hasn't arrived four working days from the date that you opened the case, and the seller has not refunded you in full in the meantime, then go back into the case details. At that point you ought to see a blue button that won't have been there before. This is the button that you can use in order to escalate the case to eBay. Click on that button and a white box will appear on the screen that you can use to submit a supporting statement as to why you are escalating the case. Once you have done that submit the details to eBay for them to review and consider. eBay don't like it when sellers fail to honour the deal and send the item, so if the seller hasn't sent the item eBay will refund your money in full.
Finally, once the case has been closed you can then leave feedback for the seller. Don't do it before - there have been cases in the past where the buyer has left feedback before the case has been closed and the seller has been able to use this as a means of persuading eBay to remove the buyer's feedback. By waiting until the case has been closed and then leaving feedback there is a far lower chance that the seller would be able to successfully convince eBay to remove your feedback, especially if you refrain from saying anything that could be consisdered to be a breach of eBay policy with regards to what you can and cannot say in feedback.
