stealing the sat nav from a 73-year-old injured pensioner 's crashed car as she waited for an ambulance .
she was waiting from an ambulance with her husband , who has dementia , when the thief sneaked into her car and stole the black garmin device from underneath the passenger seat .
a member of the public took a photograph of the suspect as he left the scene and walked across the grass with his dog at around 12 pm last thursday .