Missing Files app from dash / application switcher

I am using Ubuntu 16.04 LTS (very happy with it so far), but I am facing a really weird issue. It's not impossible that I have changed a setting somewhere to break it, but I cannot find such a setting anywhere.

When I launch the Files application (Nautilus) I do not see the application in the launcher (the left panel). When I Alt+Tab I see all other apps (except minimized), but Files is also missing. The app is not minimized.

Solution 1:

If you open Nautilus and navigate to /usr/share/applications you will see some files named 'Files'. In the Nautilus window you will not see their filenames unfortunately you will see this:

If you first drag each file onto a gedit window you will be able to identify the files as:

1. nautilus.desktop
2. nautilus-folder-handler.desktop
3. org.gnome.Nautilus.desktop

All you need to do is to drag the one named org.gnome.Nautilus.desktop over onto your left panel launcher and simply drop it there. All should be well :)