I was led to believe that Google found web pages by following links.
I made a test page with no links going to that page. It is on a brand new dot CA domain name that was just registered by me. It is hosted in a sub-folder of one of my other domains but uses the domain pointing tool to point to its own domain name.
I was doing some research on keywords and found this test page ranking fairly high (high enough to find it by accident) in the serps when there should be no way for Google to know the page exists! The page has no practical purpose yet, so I did not want the search engines to find it at this point. How would Google have found it?