<a href="http://www.cnn.com/US/9609/17/korea.pows/>Eisenhower knew POWs remained in Korea:

Newly disclosed documents suggest that as many as 900 U.S. servicemen were left behind in North Korea after the United States and North Korea exchanged prisoners following the Korean War. The declassified papers were released by the Dwight D. Eisenhower Presidential Library.

The public didn't know about those left behind, but it is clear that Eisenhower did. Five months after the war, in a document dated December 22, 1953, Army Secretary Robert Stevens met with President Eisenhower and told him the Defense Department had the names of 610 Army people and over 300 Air Force prisoners still held by the North Koreans.

This one hits close to home. My uncle, Paul Miller, was a POW in the Korean War for 30 months. He damned near died there.