If you want to search through metadata fields in a Relativity workspace, note that you may get different results searching with a keyword index than you will get with a dtSearch index. 

If a search for an entry in the metadata doesn't pop up in the available dtSearch index:

Trying switching to the keyword index, and you may get better results. 

While the fixed length text fields used for the keyword index may vary, a keyword index is automatically populated, and the selected fields will be indexed.  However, if you search for multiple terms that exist in different fields, no results will be returned.