It has been more than 10 years since Susana Trimarco's daughter Marita Veron went missing, and the pain is still raw.

"3 April 2002 was the saddest day of my life," says Trimarco. "I will never forget that day, as it was when my daughter's life was destroyed."

Last week, a court acquitted 13 people accused of kidnapping Marita Veron and forcing her into prostitution. Angry demonstrations erupted in Buenos Aires, Argentina, after the ruling. But there's a powerful story of hope behind this setback. Veron's name, and the names of hundreds of other victims, would never have been known to the court or the country without the brave actions of one woman – her mother.

A mother's crusade

The global numbers on illicit trafficking and the rape trade are unbelievable. As many as 2 million people are trafficked across international borders each year, many of them for prostitution. Add in domestic trafficking, and the number jumps to 4 million. The estimated total market value of illicit human trafficking is more than $32bn.

Trimarco's courageous story puts a human face on this monstrous criminal enterprise. After the disappearance of her daughter, Trimarco sought to find her. She successfully infiltrated gangs involved in the rape trade on the pretense of buying women. She gathered information that led to police raids and the rescue of dozens of trafficking victims. In a cruel twist of events, one of the trafficking victims freed in the first of these raids informed Trimarco that her daughter had been held in the same brothel, but had been moved before the raid.

Since she began searching for her daughter, Trimarco and the organisation she founded have helped free 400 women from sexual slavery and brought 800 cases to court. Her advocacy was also crucial to the passage of anti-trafficking legislation in 2008 that has freed almost 3,000 women from sexual slavery. Many cases, perhaps even that of Marita Veron, involve corrupt public officials, making prosecution difficult. Since the 2008 law, there have been only 71 successful convictions.

The fight goes on

Despite last week's setback, Trimarco and other advocates across Argentina continue to fight to save young women's lives. Argentinian President Cristina Fernandez reported that she spoke to Trimarco shortly after the verdict:

"I thought I would find her destroyed, but I found her more together than ever, more committed to keep fighting ... She told me 'President, don't worry, I'm going to keep fighting'."

Fernandez has now called a special session of congress to eliminate a number of loopholes in the current law that allow the rape trade rings to avoid conviction, such as a provision that places the burden on women to prove they did not consent to being sex workers.

Trimarco still hasn't given up hope of finding her Marita: "I have found victims who have been forced into prostitution for up to 12 years. My daughter can still be alive."

Sources: BBC, UN Population Fund, Nazarene Compassionate Ministries, AP