By Ishbel Matheson BBC East Africa correspondent

Just before the entrance of Kakuma refugee camp in the desert of Northern Kenya, a billboard proclaims "Women rights are human rights".

But across the barrier, in the hot, teeming warren of huts and dust roads, 17-year-old Grace Anyieth has not seen much evidence of this slogan being put into practice.

In her foster mother's compound, she picks through beans, sifting out dirt, preparing lunch.

Ayen would like to carry on with her education

She lists her chores: cooking, cleaning, washing, fetching water from the distant stand-pipe, looking after her guardian's children.

In other words, she is an unpaid servant.

Grace and thousands of other Sudanese children - most of them boys - staggered out of their war-torn homeland to Kenya in 1992.

They had an extraordinary story to tell.

After their parents had been killed or lost in the mayhem of the civil war in Southern Sudan, the children spent years wandering through conflict and famine, dodging armies, militias and animal predators, seeking a place of safety.

New start

It was an epic march, which captured the attention of the world.

But while many of the boys - who became known as the "Lost Boys" - were resettled in the United States, the girls' claim for equal treatment was overlooked.

"Why not the girls?" Grace asks, "I would have liked the chance to go abroad. You can be free there. Free to work, free to study."

In our culture, women are being dominated Grace Anyiek 'Lost Girl'

Few have thought to inquire about the fate of the "Lost Girls".

Although an estimated 3,000 arrived in Kakuma in 1992, most have simply vanished from official records.

We find Ayen at school in Kakuma, listening to a lesson on human rights.

A tall, striking, young woman, Ayen would like to continue with her education.

But at 18, she feels time is running out.

"The problem is that my foster-parents could find a rich man, and then they will marry me off . Even if I don't want to go, they will insist."

The boys and girls were separated as soon as they arrived in Kakuma in 1992.

Valuable brides

The boys were kept together as a group, living in villages within the camp.

According to Sudanese custom, the girls were placed with guardians who were supposed to protect them.

But many foster-parents - it seems - did not have the girls' welfare at heart.

In a place where poverty is rampant, young women are a valuable commodity.

They can be sold off for a good bride-price.

When international attention focused on the lost boys, the Sudanese community kept the girls away from the limelight.

They have lost that status of 'Lost Girls' Kofi Mable UNHCR

Sudanese leader, Gideon Kenyi, says, "The issue of dowries had become a priority to the people who are owning the girls. They see the girls as a way of generating wealth, by marrying them or by giving them to someone rich."

Refugee workers from international agencies assumed that the girls were safe, because they were being sheltered by their own people.

That assumption has turned out to be wide of the mark. But the head of the UN refugee agency in Kakuma, Kofi Mable, is doubtful that the girls can be helped now.

Living in fear

Most no longer meet the strict resettlement criteria demanded by host countries, for single, unaccompanied minors.

"We have lost them... they are completely lost", Mr Mable says regretfully, "They have lost that status of lost girls. Some of them are mothers. They are married...There's nothing I can do - or anyone else can do"

But it is clear that some of the 'Lost Girls' continue to suffer greatly.

Aluel's two year old daughter, Monday, clings smiling to her knee. Aluel herself rarely smiles.

Single mum Aluel is forced to live as an outcast

She recounts quietly, how she lived with an elderly guardian when she first arrived in Kakuma.

One night a man crept into her hut and raped her.

As a single mother, Aluel is now reviled by the Sudanese community, living as an outcast, terrified of being attacked again.

Aluel's case is not isolated.

The findings of a recent study suggest the camp is not a safe place for young, orphaned girls. Sexual abuse, forced marriages and beatings are common.

Dr Pauline Riak of the Sudanese Woman's Association describes Kakuma as a prison, where young, women are especially vulnerable.

She thinks the Lost Girls can be traced and helped, if international agencies like the UNHCR are determined to do so.

Miserable future

"Human beings should be treated equally. If they can go to a better life, then they should do."

Few of the girls have the chance to study

But as time passes, the chances of the girls ever leaving Kakuma recede.

Grace Anyiek heaves a heavy Gerry can of water onto her head, and describes her future frankly as "miserable".

The bitter irony of the "Lost Boys" good life in America is not lost on her.

"In our culture, women are being dominated. Not just in Sudan, but in all of Africa. Maybe people don't think we did much, because they see us as followers of the 'Lost Boys'."

"But the fact remains ladies were there."