Thousands of refugee children have gone missing after arriving in Europe. How is that possible? Why does no one know where they are and what happened? And why doesn't anyone know exactly how many there are? Two years ago, Europol named the number of 10,000 missing refugee children. It was an estimate. They fear the children will become victims of criminal networks. Yet nothing has changed since then. In fact, this week, Europol reports that there is still no insight into the number of refugee children who are victims of human traffickers. "But a future increase is expected." How can thousands of children just disappear in Europe? And does this also happen in the Netherlands? The international journalist collective 'Lost in Europe' is looking.