The "destroy", destroys the object you are working on.
well - the destroy behavior is obvious now, after the fact. Anyway, for what it is worth, I can't think of any real use case where I would want a portal site to have no 'default' page, thereby leaving all people that visit the home page for the portal with a 404 error...
How do I recover from this?
Can you create a new page named "default"?
I suppose I can, but I think the functionality of 'destroy'ing a page is questionable. I can see the potential value of being able to destroy pages...however, I think there are some pages that must be 'golden' in the sense that they can not be deleted - like the default page for the portal. Also, some portlets, like the admin/mgmt portlets probably should be 'golden' otherwise a careless click of destroy (like mine) results in an unusable portal. I think I am going to have to reinstall my portal instance in order to get back that default page.