This is a very frequent question. EBay has GOT to make viewing a guest order easier because the continued impossibility of it is stressful and annoying for users, and that's not the best way to get people to want to come back. Here is what the eBay help pages say about buying as a guest:
According to eBay:
You can buy some items without registering as an eBay member, by using Buy It Now, and you can see your order details by following the link in your confirmation email. On the order details page you can see your purchased items, shipping status, and tracking numbers, return an item or report that you didn't receive an item.
http://pages.ebay.ca/help/buy/buying-as-guest.html
How to register:
http://pages.ebay.ca/help/account/how-to-register.html#steps
