It may not be advertised widely, but zeitgeist + journal might help save your behind when you're in a hurry and can't find a file.
aptitude show zeitgeist
" Zeitgeist is a service which logs the user's activities and events (files opened, websites visited, conversations held with other people, etc.) and makes the relevant information available to other applications."
And that it does. A service without an interface isn't terribly useful -- so you will want to install gnome-activity-journal as well.
Chances are that zeitgeist is already running on your system, so that you only need to install gnome-activity-journal, which is present in the repos, and then you'll get access to all the old data you've been accumulating.