It was the first release of a Western hostage in more than three months.
Iranian officials have said they would use their influence to help free the Western hostages only if the four were found.
They also urged kidnappers holding Western hostages to free the men.
But, all too quickly, there were again 12 Western hostages in Lebanon.
Israeli officials have said the air strikes were unrelated to the possible release of Western hostages.
Some Western hostages kidnapped during the mid-1980s were held until June 1992.
The situation remained bleak for other Western hostages being held in Iraq.
Ten Western hostages are believed to be held in Lebanon.
They said they believed that the time was right now to end the situation with all the Western hostages.
He said later that "a positive trend has evolved" toward freeing Western hostages.