There are about 2,200 servicemen missing in action from the Viet Nam War. And 5,000 from the Korean War. These figures are dwarfed by the 79,000 missing from WWII, half of which are deemed "recoverable", i.e. not at the bottom of an ocean. Today WWII MIAs are still found around the world but not at a significant rate; the US ceased looking for its missing in the 1950s so those found today are by chance or through private efforts.
Which brings us to the one in 79,000. In 1953 a British long range desert patrol in Libya came upon human remains in the Sahara desert. Believing them to belong to an Arab nomad, a single photograph of the remains was taken before they were buried in place.
Six years later, the wreckage of a USAAF B-24 bomber was found in southern Libya, its crew absent. After several searches, eight of the bomber's nine crew members were found in a rough line drawn northward from the crash site, the last group over 100 miles from the wreck. It was later determined that the crew of the bomber, nicknamed The Lady Be Good, had bailed out approximately 15 miles north of the aircraft's final resting place and then trekked northward to the African coast, unaware that they were deep within the continent's interior. Doubly tragic, when they had bailed out they believed they were over the Mediterranean Sea so had left behind their desert survival gear (in the dark the desert was indiscernible from the sea).
The fact that some of the crew had walked over 100 miles with almost no water confounded survival experts at the time. Further, it was ascertained from a diary that a ninth crew member, gunner Sgt. Vernon Moore, had walked farther in search of the coast. His remains were never found.
Or were they? Although the skeletal remains found by the British in 1953 weren't precisely plotted, they were in the area north of the Lady Be Good's position. Later forensic analysis of the single photograph taken regarding ethnic origin was inconclusive....
To this day we tell servicemen that no one is left behind. It's not true.