Akhmed Abdul Qader was one of the most famous detainees in Guantanamo Bay during the 13 years he was imprisoned there. He was 18 when he was arrested in Pakistan and, while he had stayed at a guest house affiliated with the Taliban, there was no evidence he had ever so much as fired a gun.

And now – perhaps unsurprisingly for someone who's finally free after 13 years in prison – he's nowhere to be found.

Mr. Qader was cleared for release in 2009, but because his home country, Yemen, was in turmoil, he spent another six years in detention in Guantanamo while the U.S. government looked for a country willing to resettle a man who had nearly spent half his life in the company of military interrogators and other suspected Taliban and al-Qaeda members.

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Earlier this year, tiny Estonia – nervous about a newly aggressive Russia to its east and anxious to build up favour with the United States in case of a confrontation – stepped up and agreed to resettle Mr. Qader. Asked why her country's government made the decision, Merle Maigre, security adviser to Estonian President Toomas Hendrik Ilves, is blunt. "Solidarity with the U.S.," she shrugs.

But where is he now? Ms. Maigre shrugs again. "I haven't heard much since he arrived," she says vaguely, directing the question to another government department. "There hasn't been much in the news about him."

That's an understatement. There hasn't been a single report in the Estonian press about Mr. Qader since mid-January, just days after he landed in the country. Some of Estonia's top investigative journalists say they've tried looking into what happened to Mr. Qader after he arrived, but couldn't find a trace of him anywhere.

The truth is that he could be anywhere from Helsinki to Gibraltar.

It shouldn't have been hard to track down Mr. Qader in Estonia, if he were still in the country. The country has few visible minorities, and its Muslim population is small enough to be serviced by a single non-descript mosque on the outskirts of the capital city of Tallinn. But the Estonian Islamic Cultural Centre wouldn't have been a comfortable place for someone seeking peace and solitude after 13 years in Guantanamo Bay.

Just a week after Mr. Qader arrived in January, the mosque became the focus of intense local media attention after a 31-year-old attendee was reported to have travelled to Syria to fight alongside the Islamic State group.

Estonia's Interior Ministry has held a single press conference regarding Mr. Qader's case. In January, domestic security vice-chancellor Erkki Koort told reporters that the ex-detainee (he refused to confirm Mr. Qader's name, even though it was widely known) had been provided with an apartment and a dedicated social worker.

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Mr. Koort said Mr. Qader spoke English, but no Estonian, and had expressed a desire "to leave the former life behind. He does not want to communicate with former acquaintances, nor with people he was with at Guantanamo. We don't know that he is too eager to communicate with his family."

Mr. Koort said Mr. Qader had formally applied for asylum in Estonia and had been given a three-year residence permit.

That may explain why Mr. Qader is so hard to find in Estonia. A person with a residency permit in one member country of Europe's Schengen Area can travel visa-free to any of the other 25 countries.

@markmackinnon