In My documents/Protected you can view a list of all the documents you have protected, even if they have been sent or deleted from your PC.
You can filter by date or search by document name, protection, etc. in the free-text search box.
The file type, name, protection used to protect it (Custom if it was a custom or one-time protection) and date it was protected are shown for each document you have protected.
Click on the document name to access the document information.