Now Google had refreshed and cannot update the page 3, so the snapshot is gone. I will strike it out. Even if you use the Cached Snapshot of Page feature within PageRank in the Google toolbar, it will not match documents.

At least you got the first two pages. It is now too late for page 3... Periodically, as Google "crawls the web", it visits the same or new websites and saves (updates) a snapshot of the webpage. If the site is unavailable or it sees some error message, then the snapshot will no longer be available.