old contact shows when switching to mail app

When I switch to the mail app (when it's already open and on a message but in the background), in the brief moment before the current email redisplays on the screen -- a screenshot of an old, deleted contact shows. Obviously the old screenshot is stored somewhere because it's always the same one -- one that's been deleted from my contact list for months. It's frustrating to see a name of a former business associate from the past pop up, even briefly. How can this be changed? There must be somewhere these icon images are accessible -- to be changed, deleted or regenerated.

Using iOS7 on an iphone 4S.