By Phil Stewart and David AdamsWASHINGTON/MIAMI (Reuters) - His release from a Cuban prison has been as cloak-and-dagger as his spying career ever was.Not even the family of Rolando Sarraff Trujillo appears to know what has happened to the Cuban man believed by some to be the U.S. informant secretly freed in a prisoner swap between Cuba and the United States that was announced on Wednesday."All I can say is that ... my brother has disappeared," his sister, Vilma Sarraff Trujillo, said by telephone from Spain on Friday, noting that Sarraff's family in Cuba has not heard from him in days and has not been able to pry any information from Cuban officials. "We don't know anything."Unlike the televised homecoming of Alan Gross, the former U.S. aid worker who became a household name in diplomatic circles, the United States and Cuba have declined to publicly disclose the identity of the freed spy.The White House and U.S. intelligence agencies on Friday declined to confirm or deny media reports that Sarraff, who had been in a Cuban prison since 1995, was indeed the freed spy.There's good reason why he might be out of sight."He's probably in some very quiet place being debriefed. They want to know exactly what happened," a former senior U.S. intelligence official said. "It would be a standard thing."The U.S. Director of National Intelligence's office credited the unnamed freed spy as having been "instrumental in the identification and disruption of several Cuban intelligence operatives in the United States."Chris Simmons, a former senior counter-intelligence official at the Defense Intelligence Agency, described Sarraff - familiarly known as "Roly" - as a cryptographer who worked for Cuba's director of intelligence, citing accounts from Cuban defectors.He said Cuba communicated with its spies through short-wave radio, using groups of numbers to send coded messages. Sarraff would have been able to help the United States break that code."Roly was arrested in 1995. Almost immediately the FBI can read Cuban communications," Simmons said, saying he believed Sarraff was the one released based on the U.S. government's description of the spy's work.Simmons said Sarraff worked in a three-man CIA team that included Jose Cohen, who told Reuters he escaped from Cuba in a raft in 1994. Cohen, who now lives in Miami, declined to discuss Sarraff's case in depth, though he offered a different account of Sarraff."It's very dangerous to talk about this. The press has got it wrong. Rolando and I studied together. He studied journalism. I am the cryptologist. I studied mathematical cryptology,' he said in an interview.Sarraff's family in Cuba declined to speak to Reuters and his sister did not discuss her brother's past - much less confirm any espionage work.President Barack Obama hailed the unnamed spy as "one of the most important intelligence agents that the United States has ever had in Cuba."The U.S. Director of National Intelligence's office said the informant also provided information that led to the identification of a Florida-based cell of five Cuban spies as well as Ana Belen Montes, a Defense Intelligence Agency official and one of the highest-ranking U.S. officials ever proven to have spied for Cuba.Still, Obama acknowledged that the spy's sacrifice had been a closely held secret "known to only a few."Even former U.S. officials closely engaged on Cuba policy acknowledged that they never heard of the case before Wednesday.Bill Richardson, a former U.S. ambassador to the United Nations, told Reuters he knew nothing of it when he visited the island in 2011 to try to win the release of Alan Gross."That was a real surprise to me," Richardson said. "I never heard of this. ... I even think a lot of people in the government didn't know about it either."(Additional reporting by Daniel Trotta in Havana and Julien Toyer in Madrid; Editing by Leslie Adler)Join the conversation about this story Click here to read full news..