As long as it is not connected to the other stuck joints of pipe below the free point, every joint of pipe above the free point is free, meaning it can rotate freely and be inserted and removed from the hole. Holding a string in your left hand can help you envision this. Grab the bottom portion of that string with your right hand. Since you can move the string in any direction, the middle two-thirds of the string above your right hand would be regarded as free. Since no matter what you do to the free string, it will not impact the string inside or below your right hand, the segment of string inside and below your right hand is trapped.