The Outlook 2013 client will not find results when performing a search, or it has issues when attempting to search.
To resolve the issue, please follow the steps below to re-build the Outlook Index.
1. Click on File > Options;
2. Select Search in the menu on the left, then click Indexing Options;
3. This will open the 'Indexing Options' window, click Advanced;
4. Click the Rebuild button in the advanced options;
Outlook will then rebuild its search index. This can take a while to complete, but you can continue you use Outlook as the process runs in the background.