The unindexed search indicator is represented by notes=U.
In an unindexed search, the database is searched instead of the index file. Unindexed searches occur for the following reasons:
The all IDs threshold was reached in the index file used for the search
An index file does not exist
The index file is not configured in the way required by the search
An unindexed search indicator is often accompanied by a large etime value because unindexed searches are usually more time consuming than indexed searches.