Police said they think Nicole Carmon believed her child could still have been in that car.
The confused 911 call came in Saturday morning.
Nicole Carmon told the dispatcher she'd been in a car accident sometime the night before, according to police. She didn't know where, she didn't know when, and she couldn't recall how she got home, officers told the Denver Post.
Nor could she find her 2-year-old son, she allegedly said.
Officers in Westminster and neighboring Thornton, Colorado, fanned out in both towns to search for the boy. After more than an hour, around noon, they came across Carmon's green 2013 Ford Fusion in the parking lot of a Thornton strip mall, police said. The vehicle was covered in snow, they said, and showed no signs of having been in an accident.
Inside, they found the child - "in a state of severe hypothermia," but alive, police told the Denver Post.
The 26-year-old mother was arrested on a felony child abuse charge, the Denver Post reported, and was held at the Adams County Detention Center. It was not clear Monday if she had retained an attorney or entered a plea.
Police told CBS4 that the child had been left alone in the car for at least seven hours as temperatures dropped below zero overnight and snow piled up.
"The car was blanketed with snow," police spokesman Matt Barnes told the Denver Post. "There was no way of seeing what was inside."
Medics took the boy to the hospital, where he was treated for hypothermia and frostbite. As of Sunday evening, he was expected to live, CBS4 reported.
Police said they were still trying to determine why the child had been abandoned in the car.
Andrew Duran told KMGH he had just finished his shift at a nearby restaurant when he watched police carry a motionless child out of the vehicle.
"We saw cops everywhere," Duran said. "All of a sudden, you see cops pull out this kid."
Jeanette Fam said she was working at American Nails salon when police arrived.
"I don't know how someone can forget a child," she told KMGH.
Breanna Sanchez, an employee at one of the businesses in the strip mall, told FOX31 that she noticed Carmon's car parked in the lot when she arrived at work around 9 a.m. Saturday morning. She said she noticed the parking lot swarming with emergency workers a few hours later.
"I can't imagine staying in a car overnight. I'm freezing just standing here," she said. "I feel really bad that he sat there all night."
(This story has not been edited by NDTV staff and is auto-generated from a syndicated feed.)