Activities Search excludes records with no targets

Might be two issues here. Noticed this searching for Membership Signup activities. If a membership signup is done offline, the membership is added and a membership signup activity is created. The activity is ASSIGNED to the contact to whom the membership was created. But the activity has no WITH CONTACT value. First, shouldn't it still show up in an activity search? Second, shouldn't this particular type of activity be generated WITH CONTACT being the contact who received the membership and NOT assigned to anyone?