@Reminiscence- That's a tough story to read. I'm sorry for your family's loss. My dad was listed as missing in action during Vietnam, but we didn't want to believe it. He was a helicopter pilot, and the military usually knew where something as big as a chopper was headed. We didn't think he was dead, but we also didn't think he was actually missing, either.
As it turned out, he was captured by the Viet Cong after his helicopter crash landed on the way to a pick-up. He was held in a POW camp for a year until it was abandoned for unknown reasons. The status "missing in action" can give families hope their loved one is still alive, but in my experience the status is more often changed to "killed in action", unfortunately.