to enable search on custom aspect data (Dublin Core is a "custom" aspect as in "additional" to the core data set), you need to define the relevant advanced search form in Alfresco Share. Otherwise you will only be able to find objects via the quick search Google-like syntax. Have you had a look at <a href="http://wiki.alfresco.com/wiki/Share_Advanced_Search">the Advanced Search wiki article</a>? This should help you get started.
Thanks for the link - Long term and for user usage you do need a custom advanced form. you can also search for the item based on the content model example cm:identifier:KB0000002 gave me the result I wanted.
so I see the path now, thanks so much for your input.