You can just click the option against your item listing to cancel the transaction. You have to explain (from a list of options) why you are cancelling and want to relist - you will get your final seller fee credited from eBay.
You only open an unpaid item dispute if the buyer is going to pay, which they are obviously not in this case.
If there was someone bidding against your (non-)buyer, once eBay has agreed to cancel the winning bid then you can offer the item to the second highest bidder, to see if they still want it.