Thanks for the story, I am one of the "few" who had not heard it.
Not knowing your age, I don't know if I need to impress upon you how tremendously unpopular the Vietnam War was for most Americans. In addition, Watergate was undermining the credibility of a government that had promised to end the war. I remember this time period quite well and would have to agree with Col. Matejov:
"Baron 52 was shot down right before the North Vietnamese were about to release 591 POWs. The American government, he believed, did not want to endanger the release by asking Vietnam for four more."
No, I can not contribute any verifiable evidence or fact to this conclusion. And I can only sympathize with the many families who suffered due to this conflict.
Jack