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to help your internal page stay indexed you should make sure it has significant content that is unique. then make sure it has inbound links from other websites.
as your testing methods, site: search is not always accurate, link: search is even worse. toolbar pagerank also has accuracy issues.Thanks again. I realized the inaccuracy of link: and toolbar page rank but didn't know there were problems with site: search. I also check by searching a quoted paragraph of text, and the page is not in the index.
the foolproof way to know your page is indexed by google is to look at your logfiles and see if google is sending traffic to that page. otherwise i would search for unique string of text that you add to that page.
You can rule out a technical issue by using the "Fetch as googlebot" tool in WebmasterTools. If the right content comes back, then the cache: issue is just a reporting bug. However, if you get back the home page, it's time to start digging.