When you coordinate to the driver and your driver picks your call and confirms that he has found your item in the car, then you plan a proper time and place to meet for the return the item.
15$ fee is charged to you once your lost item is returned. Uber is a worldwide transportation company so the fee gets change in every country. Uber take this fee as the compensation because driver make some time for you and deliver your lost item. It was your fault to loosing the item in Uber car.