Four-year-old Ellery Chartier-Molinari sat forgotten in a parked school bus for three freezing hours Monday night while her mother led a frantic search across Windsor, Ont., and the outlying area.

The kindergartner had fallen asleep on her bus as the driver passed by her daycare, completed his route and parked in a locked yard far from her home.

When Ellery woke up, she was alone.

Her mother JoAnne Chartier finished work and arrived at the daycare around 5:30 p.m. ET. She looked around as other parents picked up their children with a hug and brought them home, but Ellery was nowhere to be found.

She approached the staff member responsible for getting kids off the bus and asked where her daughter was.

"I was told, 'She didn't get off the bus today,'" said Chartier. "I said, 'What do you mean she didn't get off the bus?'"

JoAnne Chartier, right, called police and posted on Facebook about her missing daughter after she realized Ellery hadn't got off the bus at her daycare. (JoAnne Chartier)

Family used Facebook

With a sickening feeling sinking into the pit of her stomach, Chartier started calling anyone who might know where her daughter was — her school, the bus company, the police.

"It was a parent's worst nightmare," she said. "I had no idea where she was or even how to find her because the bus company was unreachable."

Her sister turned to a Facebook group of "about 5,000 moms" who quickly spread the word that a girl was missing and her mother was desperate to speak with someone from CG Pearson Bus Lines Ltd.

The family turned to Facebook in desperation after calls to CG Pearson Bus Lines failed to connect them with any staff members. (Jillian Barrie/Facebook)

The post reached a woman who worked with the company and helped put the family in contact.

Police officers and Chartier's brother-in-law rushed to the yard where the bus was stored, but were stuck at the gate until someone let them in.

Inside, they, and several Pearson employees who had arrived moments before, found the little girl "shaking and cold."

We will do everything in our power to make sure this never happens again. — Ryan Pearson, CG Pearson Bus Lines

"Ellery said she was sitting on the bus and was being quiet because you're supposed to be quiet on the bus," explained her mother.

Transportation manager Ryan Pearson confirmed a child had been left on a bus Monday after the driver broke the company's policy by failing to complete a "child check" before leaving his vehicle.

"The immediate response was to obviously make sure the child was safe and to get the child back to their parents safely," he said.

Company promises changes

The driver, who had 16 years of experience, was fired Tuesday, according to Pearson.

"Our drivers as a rule are very good people who are very conscientious of what they do," he added.

"All of us are really, truly sorry for the incident that happened and we will do everything in our power to make sure this never happens again."

Ryan Pearson from CG Pearson Bus Lines said the driver should have done a walk-through after the run and has been fired. (Melissa Nakhavoly/CBC)

Pearson's policy currently states drivers must check the bus after "each section of their run," said the manager, who added the company held a meeting with its drivers Tuesday to talk about the seriousness of forgetting to check for children.

Starting today, Pearson is looking at ways to make emergency numbers easier for parents to find and now requires employees to radio the dispatcher to confirm a check has taken place.

If there's a child trapped on the bus … you should be reachable. — JoAnne Chartier

Ellery was "really brave," according to her mother, who said she broke down when the two were finally reunited.

"I was crying, we gave each other a big hug and she wiped my tears."

'It's too late for us'

The little girl had some trouble falling asleep that night and her mother said she was nervous about getting on the bus again Tuesday.

Chartier was dealing with some feelings from the previous day as well.

"The feeling of not knowing where your child is the worst feeling in the world," she said. "She's four years old."

Chartier is planning to take legal action against the bus line and daycare and credits her sister's use of Facebook as the only reason the search for Ellery didn't last hours longer.

"If there's a child trapped on the bus because your employee didn't check, you should be reachable," said Chartier. "I'm glad they're doing something now, but for us it's too late."