Help! Search Engines Are Keeping Me Boxed

Anyone would want to be included in the top result of search engines like Yahoo and Google. That is why I was glad to learn that I ranked 4th in a certain string of keywords in Yahoo. However, a question popped out of my mind after I noticed that the search result is pointing only to my index page,

“What if after a few more posts and that topic is no longer available in my index page, will my site still turn out in the search result for that same string of keywords?”Logically, I think it will no longer show. If it does, my visitors might not be directed properly to view that specific posts of mine. I would really want the results to point directly to my post’s permalink like it did to the #1 and #5 result in the picture above. I just don’t know how.

If anyone out there can clarify this confusion of mine please, shed me some light.