On December 20, 1980, Hilliard was involved in a car accident that resulted in car failure in cold weather. She walked to a friend's house 2 miles (3.2 kilometres) away and collapsed 15 feet (4.6 metres) away from the door. Temperatures dropped to −22 °F (−30 °C) and she was found "frozen solid" according to witnesses at 7 a.m. the following morning after six hours in the cold, though doctors say her stiffness was likely due to powerful muscle contractions rather than actual freezing. She was transported to Fosston Hospital where doctors said her body temperature was too low to register on a thermometer. Her face was ashen and her eyes were solid with no response to light. Her pulse was slowed to approximately 12 beats per minute. [4] On arriving at the hospital Hilliard was wrapped in an electric blanket. Two hours later, she went into violent convulsions and regained consciousness. Her only injuries were frost-bite, which were treated with skin grafting.[3]

Commenting on the case, Dr. Richard Iseke, associate director of the Boston Emergency Medical Center said, "Although Hilliard is undeniably lucky to have survived, there are numerous case reports in the [medical] literature of people who have survived [with interior body temperatures] as low as 68 or 69 degrees Fahrenheit [20 or 21 degrees Celsius]." Dr Richard Young of the Hershey (Pa.) Medical Center said that frigid temperatures actually protect some people, such as those who appear to have drowned but are revived after being pulled from icy water with no pulse or respiration. Such survivors sometimes show temporary mental impairment but recover with no permanent damage. "We believe hypothermia gives the brain added protection. It puts it in sort of suspended animation," he said.[3]