I've found a solution for this issue today, so I thought I would pass it along. Cumulative update package 3 for SQL Server 2008 Service Pack 1 addresses SQL Bug #316148 (KB 967552): FIX: SQL Server 2008 Database Auditing shows query criteria as a parameterized value instead of the actual record.

I installed the hotfix on our dev server, and found that the actual search predicate is now being included in the audit statement capture.

The fix link is http://support.microsoft.com/kb/971491/LN