I downloaded the program and ran the scan for drive C. It returns a message no files found that match filter. I'm looking for a document, so I typed that as a filter and word file name ext.
Please help I need a very important doc for law enforcement
Then do it properly and employ a reputable auditable data recovery service. In any event it sounds as if you're using Recuva in a business environment, which is not permitted by the licence agreement.
if you perhaps mean the document is needed to prove something, not for you being a legal forensic law enforcement person, try the scan without the filter. then (maybe) filter after the scan has finished. This will allow all deleted files to be found. At times the scan won't find the exact name because either it's a little different or it has been overwritten slightly, such as the highlighted items in the picture below