Hello,
Actually, this should be quite straightforward.
If you go into the Preferences, and highlight “Reference Types”, in the lower left-hand corner should be an EndNote Defaults button. This button resets the currently select section of Preferences. So, clicking it isn’t going to do anything except to restore the Reference Types to their default installation settings.
Other groups of preferences will be unaffected by this.
That should allow you to get back those original Reference Types.
I do hope this helps.
Thanks!
Steve