A 17-year-old boy is brought to the emergency department after sustaining a high impact injury to his arm during a baseball game. He reports being hit in the right shoulder with a batted ball, causing immediate pain and swelling in that region. Physical examination of the right upper extremity is limited by the patient's pain, and full motor and sensory examination are unable to be performed. X-ray of the shoulder shows a fracture of the surgical neck of the humerus. Which of the following additional finding will most likely be seen in this patient?