Agreed.

The xaml page is what is packaged up and placed into the XAP file, and it is the XAP file that is loaded onto the page. You are going to need to re-direct to the page hosting your XAP file, and then, within the load event of the main App.xaml page, you could inspect the query string, to decide what "page" within the XAP file that you want to display.

Gary