Why when I use the search feature it doesn't  include all the books.  Example:  Heartsong Presents Mysteries search only brought up 2 books when in fact there where 8 of them on the bookshelf.  I have notice this on many occasions that the search doesn't always show everything. 

Why?

The most common reason why all books wouldn't show up is that your search is for Posted books and thus would not include unposted, unavailable titles.  Be sure your search is for "All Books" and not just "Posted Books".  However, that wouldn't seem to be the case in your situation, where you are looking for books you know are already posted...

 The next most common reason is that the books not showing up do not exactly match your search parameters.  Just using your example, if you search for Heartsong Presents Mysteries that search most likely would not show books that have Heart song with a space between the words, or ones that just say Heartsong Presents without the word Mysteries.

And sometimes, it is just a glitch of the way the Search engine functions.  It has a way of adding books you'd never expect, and sometimes, excluding books you would expect to be included...

You can help improve the search function by submitting data edits to correct mis-spellings, add series info etc...,

Sometimes it helps to widen the scope of the search, for example by just submitting "heartsong".  Or, maybe it's a glitch.