deadbeat friend
An unrestricted friend who chooses not to be a regular or supportive fixture in lives of people they call friends; a friend who is MIA for long periods of time then shows up and acts like nothing has happened to interrupt the normal flow of the friendship.
Sandra and I had coffee the other day after not communicating with each other for seven months. She picked the conversation like we had only gone a week without talking. She is such a deadbeat friend.