Cox's Bazar, Bangladesh (CNN) In the middle of the night in a town in south-eastern Bangladesh, a Rohingya boy is found bound and blindfolded and dumped in the marketplace. He is pale and skinny, but he is alive. And nearly four months after he went missing, that is enough for his parents.

In April, Mohammad Faisal vanished from Kutapalong refugee camp in Cox's Bazar, Bangladesh where he lived with his family. His parents feared their boy, aged about 13, had been trafficked onto a fishing vessel, or perhaps worse.

Child trafficking has become common in the refugee camps of Cox's Bazar. The largest refugee camp complex in the world is home to hundreds of thousands of Rohingya Muslims who live in temporary settlements after fleeing violence in 2017 that drove them from Myanmar and left thousands of Rohingyans dead . Trafficked girls may end up in a life of prostitution, boys in forced labor; many are transported to India. But Faisal's story was stranger than that.

Back in April, his mother Khurshida Begum says her neighbor's daughter and her husband, a Bangladeshi citizen, visited her home, a tiny shelter made of bamboo poles and plastic sheets. The husband, called Kamal Hosan, allegedly offered to take Faisal on a day trip to the market. "I let them go," says Begum. "I just wanted my son to have the chance to get out of the camp for a moment."

Instead, he disappeared without a trace.

A picture of Khurshida Begum's then-missing son Mohammad Faisal.

Begum says shortly after Faisal's disappearance her family received a phone call. The voice on the other end said he would return their son, but for a price: 1,000 taka -- about $12 US dollars.

For Faisal's parents it was an easy decision that came at a steep cost. In order to raise the money to buy back their son's freedom, the family sold their entire three-month ration of rice. They transferred the money, but the perpetrator didn't hand over their son, nor did they provide a location to find him.

Begum looked for outside help, but it's an uphill battle for Rohingya to have their voices heard. Getting information out of the sprawling camp often proves to be a challenge. Rohingyas need special permission to leave Cox's Bazar and, because the Rohingya are technically stateless, there's no guarantee the Bangladeshi police will file a report.

In July, the CNN Freedom Project traveled to Cox's Bazar with the Kulczyk Foundation, a non-profit group focused on providing equality for disadvantaged women and girls, to report on Begum's story. CNN followed her desperate search, witnessed the bureaucracy standing in her way and listened to the fierce advocates who had supported her.

Begum started by speaking to community advocates at the Arakan Rohingya Society for Peace and Human Rights (ARSPHR) inside the camp. Legal advocate for women and children Wahida Idris, director of the Bangladesh National Women Lawyers' Association (BNWLA), took up Begum's case in June.

After taking down Begum's testimony, Idris followed Faisal's mother back to her home to confront the suspect's Rohingya wife about Faisal's disappearance. But Idris says the pregnant woman offered little information, despite seeing Begum's pain. The lawyer recalled how the woman said her husband worked on a trawler at sea, but didn't know where he could be located. She said they could kill her, the police could put her in prison, and still she would not be able to help.

The camps at Cox's Bazar have become a hunting ground for traffickers, with recourse difficult for victims and their families.

A police report was filed but the case cooled. With little in the way of leads, the prospect of returning Faisal home began to look grim.

When CNN left Cox's Bazar in early July, Faisal was still nowhere to be found. Then on August 21, Begum's months of silent prayers were answered.

Her husband Laal Miah received a phone call with Faisal on the other end of the line. A man had found him in the marketplace and looked after him for the night. The following morning, he drove Faisal down the long, narrow road connecting the town to the refugee camps, where Miah reunited with his son. Faisal had light marks on his wrists and around his eyes, but was otherwise physically unharmed.

Still little is known about what happened to Faisal in captivity. He told CNN that Hosan led him to a room, tied him up and left him there in the dark for more than three months. Faisal did not see him again. Occasionally, a small boy would bring him food. Faisal is unsure why he was let go.

Mohammad Faisal reunited with his father Laal Miah and mother Khurshida Begum after his unexpected release.

"Faisal's case is unusual," says Idris. "He's lucky to be alive. In most cases, traffickers either sell or will kill victims."

Bengali media reported Hosan, identified by police as a member of a pirate gang, was killed in an alleged gunfight with police on August 20. Hosan's wife inside the camp confirmed his death to CNN. CNN has requested to see Hosan's death certificate.

For Begum, that matters little. Arms wrapped tightly around her eldest son, she is only willing to let go long enough to wipe away the tears of gratitude. "I want to thank everyone who helped bring my son back to me. I have no words in my vocabulary but you all will be in my prayers."

More cases every month

Refugee camps at Cox's Bazar, Bangladesh viewed from the air.

Other families are yet to receive such good news. "We have more than 400 missing persons," Mohib Ullah, president of ARSPHR, told CNN last month.

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Many cases are linked to human trafficking. Fawzia Firoze is president of the BNWLA, a non-profit legal aid group focusing much of its work on Rohingya women and girls. A week before hearing Begum's account, Firoze said her group took in seven Rohingya girls trafficked out of Bangladesh and rescued by officials at the Indian border.

Idris says "every month we receive at least 60 cases of trafficking victims who are repatriated from India," a mix of Bangladeshis and Rohingya.

A Rohingya boy looks into the camera. According to the UN migration agency, men and boys account for about a third of Rohingya forced into labor.

Bangladesh's Refugee Relief and Repatriation Commissioner Mohammad Abul Kalam says the issue of human trafficking is one that officials take seriously.

"We have alerted all the security agencies that trafficking events are taking place," he says. "We have tightened the border areas, security has been tightened on the sea and we have increased patrolling by the coast guard and the police and military are guarding and protecting this population from trafficking."

The population of the camps at Cox's Bazar is 912,000 , greater than the population of San Francisco , and Kalam says there are around 100 new births every day. That's a growing number of potential future victims caught in a political impasse.

Boys play in one of the Rohingya camps in Cox's Bazar. With 912,000 Rohingya, the camps in Cox's Bazar have a greater population than San Francisco.

For two years, Bangladesh, Myanmar and international governing bodies have deliberated over whether Rohingyas should return to their land. This month, 3,450 Rohingya have been cleared to return to Myanmar. It's still unclear, however, how many from that list would like to do so. There is real fear among many Rohingya that returning to Myanmar without proper citizenship status or security measures could make them vulnerable to the type of attacks they were subjected to two years ago.

Still, Kalam insists this is the proper course of action: "The policies pursued by (the) Myanmar government since the 1960s created a lot of discrimination with this Rohingya population. The problem was generated within Myanmar and, actually, it is Myanmar that has the solution. But it will be a global problem soon if we fail to address it properly."

All of which provides an uncertain and tenuous future for many of the residents in Cox's Bazar.

Rohingyans congregate on August 25 to commemorate the second anniversary of the widespread violence that drove them from Myanmar.

On Sunday, August 25, tens of thousands of Rohingyans convened in the camp to commemorate the second anniversary of a campaign of violence launched by the Myanmar military on the ethnic Muslim minority in the country's Rakhine State. Myanmar has long claimed to have been targeting terrorists.

Those who gathered at the commemorations wore white, chanted prayers and remembered loved ones and neighbors lost. It was also a time to look forward to more news about whether they will stay in the camp, be repatriated to Myanmar or be moved and try to make a home somewhere else. But for now, inside their sparse, oppressive shelter, Khurshida Begum and her family can only smile.