"Two missing 12-year-old girls were found "cold and hungry" after spending a night locked inside a train.
Amy Greenan and her friend were playing at Balloch, West Dunbartonshire, when they boarded a train to Glasgow on Friday.
They caught another train back but say they dozed off and woke to find themselves trapped at Helensburgh.
After waving to a passer-by the next morning, a conductor was alerted and unlocked the train to release them.
A spokesperson for train operator ScotRail said it was assisting British Transport Police in investigating the incident.
Amy's mother Bonnie-Louise is now demanding to know how two unaccompanied children were not spotted sooner or found when the train was checked.
"The girls shouldn't have done it, but they are children and children do stupid things," she said
"Any adults who saw two 12-year-olds getting off a train on their own should have questioned that."
The girls had been playing at a park near Balloch Station after school on Friday afternoon when they decided to board the train without a ticket.
Amy has since told her mother they planned to immediately catch another train back to Balloch from Glasgow Central, but a member of staff at a turnstile who found them without tickets "told them to go away".
'The worst night of my life'
Amy had a mobile phone with her, but it was an old one as her usual phone had broken, and the battery was flat.
By the time the children could sneak back onto another train, the last service to Balloch had departed.
They boarded a train that passed through nearby Dumbarton but the girls say they dozed off and woke up trapped inside the carriage at Helensburgh, about eight miles from their homes.
The girls' parents alerted police that evening when they were unable to find them in the park at the agreed pick-up time.
"It was the worst night of my life - I was driving around looking for them and phoning. The police thought they may be staying with a friend," said Amy's mother.
"My dad came round and stayed up with me through the night. We finally got a call from a police sergeant at seven o'clock the next morning... to say they'd been found. "
Ms Greenan said she did not believe the children had deliberately hidden inside the train.
"I don't see where you can hide. The train must have been checked. Why weren't they found," she said.
The children raised the alarm the following morning by waving and banging on the carriage window after spotting a teenager walking, and a conductor unlocked the train.
"They were cold and hungry. The station staff got them something to eat and called the police," said Ms Greenan.
A spokesperson for ScotRail said: "We are assisting British Transport Police with this investigation."
www.bbc.co.uk
