What version of EV are you?
you can search for categories as explained in this technote:
http://seer.entsupport.symantec.com/docs/301300.htm
How to find a message in search.asp using the Outlook category
Details:
The way to search for an email with a specific Outlook category is to use the Advanced Search.
The URL for the advanced search options page will be:
http://your_server/EnterpriseVault/search.asp?advanced
In the "Other Attribute" = "Name" type in "keys" and the "Value" must match the Outlook category needed to search through.
Note: This is case sensitive, and the message must be added to the Outlook category before the message is archived.