Lemon Flavored Sherpa

My wife took our Lexus on a road trip with some friends. One of the friends was taking her things out of the car and pulled out a long part, shaped like an elongated capital D (about 3 feet long) with four plastic knobby hooks on it. She told my wife it fell out of the car but told her she didn't know where from. We can't figure it out either. It doesn't have much of a label to indicate where it came from or how to put it back. I attached a picture. Anyone know what this is or where it goes?