This is a bit of a sanity/cleanup issue.  The case I noticed was when a user (or non-user Anonymous) doesn't have read permission, they can still find out if a card exists or not by probing.  If they don't have read for a card, the user should never get 'missing', onl y a 'deny' view.  If it is a message, they just learn that they can't read the card, whether or not it exists, or as content it is probably blank, and not the 'add link'.