Four Americans learned Saturday that they'd be freed by Iran as part of a prisoner-swap deal with Iran. Three of them -- Washington Post Tehran correspondent Jason Rezaian, former U.S. Marine Amir Hekmati, and Christian pastor Saeed Abedini -- were well-known to the public and the international news media. But the fourth man, Nosratollah Khosravi-Roodsari, is a complete mystery.

Obama administration officials refused to offer any clues about Khosravi-Roodsari's background, why he was in Iran, or why he had been imprisoned, citing privacy laws.

Khosravi-Roodsari's name doesn't appear in any news articles published before Saturday. He's practically a ghost on public records searches -- and phone listings tied to his name are disconnected. CNN's Wolf Blitzer noted on air that he had no idea who the man was, despite covering the story for months.

Amazing Nosratollah Khosravi's imprisonment in Iran appears to have never been reported. — Michael Calderone (@mlcalderone) January 16, 2016

It's still unclear when -- or whether -- information about Khosravi-Roodsari will be released, or whether he or his family plan to come forward.

Also on HuffPost: