Washington (CNN)While the families of several Americans released by Iran are celebrating the return of their loved ones, the family of an American who went missing in Iran in 2007 says the prisoner swap brought them no news from Iran or the United States about his whereabouts or his fate.
"Unfortunately, we are not able to enjoy the same joy that they have," Christine Levinson, the wife of Robert Levinson, said Monday.
"It's very difficult for our family. And especially difficult for that we were not told before this happened. We actually had to learn it on our own, watching TV," she told CNN's Jim Sciutto.
The family is desperate to know what happened to him, and what the U.S. administration can still do to win his release, Levinson's son Daniel Levinson said.
Robert Levinson not part of Iran, U.S. prisoner swap 01:07
Levinson, a retired FBI agent, vanished after traveling to the Iranian island of Kish in March 2007. His family has said he was looking into cigarette smuggling, and the FBI has said he was working on behalf of several large corporations. An e-mail obtained by the family indicated he was trying to investigate corruption involving Iranian officials.
But he was also doing independent contract work for the CIA at the time, the Levinson family eventually confirmed.
The CIA has not confirmed that allegation. But three CIA employees -- including Levinson's handler -- were eventually fired, and seven others disciplined in connection with the case, and the CIA paid the family $2.5 million to avoid a lawsuit, family attorney David McGee told CNN.
Secretary of State John Kerry said that while Levinson's fate remains unknown, the administration will not stop trying to get answers.
"I feel horrible for the family," Kerry told CNN's Wolf Blitzer. "The Iranians have agreed to continue to try to help us find the whereabouts. Whatever may or may not have happened to Bob Levinson, we are going to continue that effort."
John Kerry talks dealing with Iran, Bob Levinson 02:15
Iranian officials in the United States did not reply to an inquiry from CNN on Monday, but Iranian officials have repeatedly said they do not know Levinson's fate or his whereabouts.
But Levinson's son treats the Iranian denials with skepticism.
"I think it's very obvious that the Iranian government knows exactly where he is," he said. "Any kind of comments about locating him and cooperation is nonsense to us."
In late 2010 his family received a "proof of life" video of a gaunt-looking Levinson. In 2011, they received photographs of him with unkempt hair and beard. In the photos, he was wearing an orange prison jumpsuit, holding signs with messages including "Help me" and "I am in Guantanamo." In the video, he looks into the camera and says, "I am not in very good health," and says, "I need the help of the United States government to answer the requests of the group that has held me."
It was unclear if he was under duress, and where he was being held. In 2011, the State Department said there was reason to believe Levinson may be held outside Iran, perhaps in southwest Asia.
Iran says it doesn't have Bob Levinson 02:46
Adding to the mystery, Levinson is believed to have had a meeting shortly before he disappeared with Dawud Salahuddin, an American fugitive who lives in Iran.
Salahuddin has told CNN he was detained by Iranian officials in plainclothes and taken to be interrogated about his Iranian passport in 2007. When he was freed the next day, he said, he was told by officials that Levinson had returned to Dubai.
His story matches accounts from friends of Levinson, who say Levinson feared he would be arrested after meeting with Salahuddin.
But American officials caution they do not consider Salahuddin to be a credible source of information, because he has admitted to killing an Iranian diplomat who was loyal to the Shah in Maryland in 1980.
Iranian officials have offered to help in the effort to find Levinson. But some analysts are skeptical of Iran's claims to know nothing.
"When he disappeared, he was on Iranian soil. The Iranians cannot deny that," said former Ambassador John Limbert, who served as deputy assistant secretary of state for Iran, and in 1979 was one of the Americans taken hostage in the American embassy in Tehran.
And according to former CIA officer Reuel Marc Gerecht, now with the Foundation for Defense of Democracies, "If he disappeared on that island, he disappeared because they 'disappeared' him."
But Gerecht also believes it was unwise for Levinson to travel to Iran, given his FBI and CIA ties. "The idea that an American could go into Iran, on some type of intelligence mission, collect valuable information, and meet up with Iranians who know he's coming, is just an invitation to be bushwhacked."
The FBI is offering a $5 million reward for information on Levinson, and the Levinson family is trying to keep attention focused on his disappearance with media appearances and the hashtag #whataboutbob.
"We miss him every day," his wife told CNN, "and if he can see this, I certainly hope that he knows that we will never stop searching for him. And we will bring him home safe and sound. And that he needs to stay strong."
