If you encounter an issue where you don't see any search results, please try these troubleshooting steps:
First, log out of Audience Drill, clear your cache, and log back in.
Then, be sure you are logged into Facebook on the browser you are using Audience Drill on. (You may have to log back into your Facebook account after clearing your cache.)
If you are not in the US, please change your Facebook language setting to English (US)
Try searching after checking these three things and let me know if you still have any trouble.