Frightening statistics from Delhi's police have revealed that 13 children go missing in the city each day. Many end up as slaves or are forced to work in the sex industry in a city which is now India's undisputed kidnapping capital.

­With almost 17 million people packed into its crowded city streets, New Delhi is the perfect place for people to get lost. But some are never found again. They simply disappear.

That is what happened to Rao Kumar's 12 year old son, Ravi. He went missing one year ago when he left the house to get his bicycle, and never returned.

"I don't know who took my son away. I looked for him everywhere but did not find him," says Rao Kumar, the father of the missing child.

And Ravi is far from the only one.

In Delhi alone, anywhere from 2-5,000 children go missing every year, while in India as a whole, a staggering 800,000 disappear.

Having a loved one disappear takes a dreadful toll on families. Kumar has not been able to hold down a steady job or stay healthy. His only focus is finding out what happened to his son. But the answer is likely a grim one - most children who disappear in Delhi end up as sex workers or slaves.

"The kids are kept in places where no one will be able to find them. They're also kidnapped for the organ trade business, adoption and also for begging," says R.S. Chaurasia, chairperson of the Bachpan Bachao Andolan (BBA), a non-governmental organization in India which campaigns against child labor, child trafficking and child servitude.

Kumar's son - like most missing children in Delhi - was lured away from a poor neighborhood while he was playing. Many family members of missing people believe that they are ignored by police because they lack money or power, and many times they are told that they have to pay a hefty fee if they ever want to see their loved one again.

"I told the police, but they always say that maybe my brother is somewhere in the park or sleeping in some temple or staying at a friend's place," Ravi's brother, Noor Ali, says.

Delhi police say that while they know they face a massive problem, things are getting better.

In the past, as many as 18 children were going missing in Delhi every day. This year, that number is closer to ten.

Organizations working to help the families of the missing say that while the police need to do more, they are overburdened and understaffed.

"We also try and pressure the court to order the police to take serious steps in this issue. To watch out for the child in railway stations and bus depots," says R.S. Chaurasia.

But this comes as little comfort to parents like Rao Kumar, who feels as if he has tried everything.

"My son used to sleep on this bed with me. The house seems empty without him and I don't know where he is. All his stuff is just lying at home," he says.

Rao Kumar continues to visit Ravi's untouched bedroom every day, holding on to the memories they shared, clinging to whatever hope he can that his desperate search for the son he loves will one day have a happy ending.