[oh8eleven]

scraggly-looking vets at a gun show who were passing out literature about American soldiers who were believed to be alive in and around Vietnam.
To the best of my knowledge, in the last 40 years, no evidence has ever been found of any POW held after the war.

[.45 Long Colt]

I’m sure you are right. There may not have been solid evidence, but they believed they had evidence. They were likely hanging their hopes on suspect anecdotes.