They are not I’m afraid. The best thing to do would be to save those templates as files and store them somewhere safe.
Well they are available if you reinstall a version of ExpressionEngine somewhere say on a localhost install and then you can always get to them although you could just (if you’re not using the template group at all) change the name of the template group to something no-one would ever guess and as long as you don’t link to them online they won’t get found.
That or exactly as Greg said and use the Template Access Restrictions so that people just get redirected somewhere else if they try to access them.
Best wishes,
Mark