Final Cut X Events missing
This is just a guess, but when the projects and events folders are on an external drive, they need to be at the drive's root level for FCPX to see them.  So, when you had them on your external drive, the file path would need to be: External_Drive/Final Cut Events/YourEvent and External_Drive/Final Cut Projects/YourProject.  They will not show up any other way.

When they're on your system drive, they need to be at ~/Movies.  When you move projects and events, it's better to do it from within Final Cut (instead of Finder) because Final Cut keeps track of all of the symbolic links.  To do this, choose File->Move Project (or duplicate project, duplicate event, move event, duplicate event).