A person went to the auction house with the manuscript and other original documents including letters to and from famous people of Buck's day. Letters from U.S. President Harry S. Truman, U.S. first lady Eleanor Roosevelt and Indian Prime Minister Jawaharlal Nehru were among the items the person carried in a 1950-era straw suitcase. The auction house contacted the FBI and Buck's estate.
The items had disappeared in 1952 when they were part of a display at the American Academy of Arts and Letters Museum in New York.
Buck later wrote in her memoir she had no idea where the original manuscript went. "The devil has it," she said.
The artifacts are valued at more than $150,000 said FBI Special Agent Robert K. Wittman.
An accomplished author, Buck was the first American woman to win the Nobel Prize in Litearature, in 1938.