When a subscriber can't see an object, clearly show that they're missing the permission in the curtain UI

Summary:
Ref T13602. When a subscriber can't see an object, it's currently hard to figure it out.

Show this status clearly in the curtain UI.

Test Plan: {F8382865}

Maniphest Tasks: T13602

Differential Revision: https://secure.phabricator.com/D21547