Not too long ago, six-year-old William Yau Zhen Zhong fell while learning how to ride a bicycle - earning himself some cuts and bruises on his hands.

That was before the boy went missing on January 16.

Today, these small scars are the source of hope for William's father Yau Kok Kang, who said that these are among the few marks that can enable the public to identify his lost son.

"Aside from those marks on his hands, he has a bigger scar on his left forehead from a previous fall. He is about 70cm. Please find him for me," said Yau while describing his son.

Choking on tears when speaking, Yau, a mechanic, said that nothing was more important than seeing his second son, who the family calls 'Ah Zhong', again.

"I am scared, I don't know exactly of what. There's so many people calling me today (Jan 18) but the only call I wish to hear is from someone who says 'we've found your son'.

"The only voice I want to hear is actually from him, calling me 'Ah Pa' (dad) again. That is all I wish for. I ask God for just that," said Yau.

He said he was prepared for the worst but is encouraged by the support he has been receiving since his son's photo was uploaded on Facebook.

It was reported that Yau went missing since Wednesday at Putra Heights in Subang Jaya.

Recounting the incident, Yau said that he and his wife had just finished dinner with his eldest son, William, and his baby daughter. They stopped at an electronics shop at Jalan Putra Mahkota and left the three children in the car a Toyota Storm.

"Me and my wife wanted to have a quick look at the washing machines because the one at home was not that good anymore. We left our children in the car for awhile," he said.

Yau said that when they were gone, their daughter started crying and that his elder son tried to calm her down.

"It is then when Ah Zhong decided to leave the car and find us. Being too preoccupied with the baby, our eldest son didn't stop his younger brother from leaving the vehicle.

"When we came back, my wife asked me why is there one boy missing," Yau added.

"We search and searched everywhere...shops and streets. We asked police to help us, but there was no sign of him," said Yau, who has been searching with a team of policemen over the past two days.

Meanwhile, Subang Jaya district police chief ACP Yahya Ramli said that a team of five policemen are working around the clock and also continue to seek public assistance.

"We also deployed a K9 dog to sniff out the boy's trail. It managed to get a scent for about 200m and it abruptly disappeared," Yahya said.

"We are closely monitoring this case but we have not obtained any leads thus far. The family has not recieved any phone calls demanding for any ransom so we do not believe it is a kidnap case."

Those with any information on William can contact the Subang Jaya police at 03-56319800, Sargeant Goh Lai Thang at 012-219713, Putra Heights police head Sub Inspector Nordin Mustaffa at 012-315 0775 or Yau himself at 016-9691616.