In apple mail, with contact photos enabled next to mail subjects, one person in my contact doesn't have his picture show up In Apple mail for OSX, I have pictures enabled for both the mail list view as well as in the message itself. This works fairly well, grabbing pictures from my contacts except for one person. Their picture doesn't show up and I don't know what makes them unique.

When I click on their name and select "Show Contact Card" it shows their picture. I can't understand what conditions would cause that picture to not show up in the mail itself.
This happens when you have the contact's email address duplicated in another contact.