As the world marks Autism Awareness Day today, a Hong Kong mother with bitter experience of how little the condition is understood still dreams of her lost son almost 14 years after he vanished.
It was August 24, 2000, when Yu Man-hon - then 15 but with a mental age of two - let go of Yu Lai Wai-ling's hand at Yau Ma Tei MTR station and ran off.
It remains a mystery how the autistic and hyperactive boy managed to cross the border at Lo Wu and what happened to him after Shenzhen immigration officers tried to return him only for Hong Kong officers to turn him away.
But his mother is sure of one thing: if the border officers had understood more about his disorder he might be at home with her today.
"He didn't speak and they thought he wasn't being co-operative," she says. "He was stubborn and sometimes made surprising responses. If they were more alert, they would have sought help from a professional to handle him."
Although she has seen improvements, Yu says there is still not enough awareness of autism in Hong Kong.
Yu admits her responsibility for letting the boy slip away but is still angry with the government.
"I have never thought of giving up, because I'm his mother. I lost him. I've done him wrong," she told the South China Morning Post.
"But I'm angry with the government too. They sent him away but wouldn't take responsibility to find out the truth."
In almost a decade-and-a-half of heartbreak, Yu and her siblings have travelled countless times to various parts of the mainland in search of her son, following leads that turned out to be wrong and even fraudulent.
There were people who told her that Man-hon had been beaten to death and others who said that mainland police had sent him to the mountains.
Yu suffers from depression and has been seeking psychiatric and psychological help.
In the past two years her visits to the mainland have become less frequent as her leg pains from polio and gout have grown worse. She relies mainly on an online network of mainland parents of lost children to continue the search.
She still contacts the Security Bureau several times a year, urging them to ask mainland authorities to investigate but without receiving a definite answer.
A bureau spokeswoman said it had been maintaining contact with mainland authorities to provide practical assistance to Man-hon's family.
"It's been so many years now, I think things went wrong in a mainland police station. Otherwise there's no reason why we couldn't find him with all that we've done," Yu said. "I want to find the answer even if I have to go to the edge of the world."
She said it was difficult to be the mother of an autistic child, but even more so to be the mother of a child who is lost.
"I hope parents with autistic children will stay strong. Though we face difficulties, like people's impolite stares, they are our children. We have to love them."