CHICAGO (CBS)–A mom from suburban Wheaton is demanding answers after her autistic toddler wandered out of his preschool and was picked up by a stranger.

The little boy’s family says they moved to Wheaton so their child could attend Jefferson Early Childhood Center, a school held in high regard for providing quality care and education for special needs students.

But after her son was found on the street by a stranger, the child’s mother says she’s extremely disappointed.

“I just hope that we get some answers,”said the child’s mom, who asked to be anonymous.

autistic child wanders away Autistic Child Wanders Away From Wheaton School

The child somehow walked away from the school playground and was missing for about 20 minutes before he was discovered by a man who spotted him on a busy street and put the child into his vehicle.

The man took the child back to the school and returned him to staff, who had been searching for him.

“It’s been a nightmare–a nightmare (of) repeating emotions and sadness and anger, the mom said.

The identity of the man who found the child is a mystery.

Adding to that mystery, the school gave the mother a bag of her child’s wet clothing–covered in mud–with no explanation of how his clothes got so dirty.

A statement from Wheaton police and School District 200 said, “This is the first time a situation like this has occurred at Jefferson and we are doing everything we can to ensure this does not happen again.”

“I definitely hope it never happens again to another family (or) another child,” the mom said. “It could’ve ended up way different, and I still don’t even know what exactly happened.”

“I know if I were in their situation, I would definitely want to know–I’d want to know,” she said. “I’m extremely disappointed that this happened.”