Whenever competency of searching for a person is discussed I always think back to a case on here, some of the more frequent older ws members may remember it.
It was an a woman and husband (and maybe her son?) In Scotland. They had CCTV of her last sighting walking by herself but couldn't find her anywhere. They had both police and civilian searches going on. The husband actually flew back to America.
The case was solved when she was found, largely down to this website in fact, when a friend of hers from America teamed up with someone from ws and flew to Scotland. They undertook their own searches with the ws goers dogs and found her, sitting under a tree.
She had remarkably been missed in all of the searches despite being in the searched area. Unfortunately she had passed (if that wasn't obvious)
But it goes to show, even when someone is essentially hiding in plain sight, they can be missed in various professional and non professional searches. Which is why it sticks in my brain.
I wish I could remember the poor woman's name.