I'm a psychiatric nurse and early in my career, I worked at a residential mental health facility. One of our residents was an elective mute, which means that he didn't/wouldn't/couldn't talk, but there were no medical reasons as to why. He had spoken earlier in his life and in fact seemed quite normal back then, with the exception of being close to seven feet tall. He'd been raised in the Deep South and joined the military when he was 19, but one night he vanished. He was declared AWOL, and eventually he was declared missing and dead.
Ten years later, a seven-foot tall man walked into a VA Hospital emergency room in my part of the Midwest and said to the receptionist: "My name is Marion Duchene (not the real name), and I've been dead for ten years."
Those were the last words he ever spoke.
He was covered with dust, and he was wearing the same clothes he'd been reported to be wearing the night he vanished. His social security number had not been used and he had no identification on his person. However, they were able to identify him, I guess via fingerprints. The family was notified but they said they had already grieved their lost man and that whomever was claiming to be him simply could not be. They demanded not to be contacted again.
Marion paced all day every day, moving his mouth that looked like talking or muttering, but no sound came out. He had an unnerving habit of throwing his head back with his mouth wide open as if he were laughing heartily, but not even a breath could be heard. If I talked to him, he appeared to listen, periodically throwing his head back in that laughter-mimicking way of his.
Various medications were tried, but they did not affect him either positively or negatively. Occupational therapy did nothing because Marion would just grin and unless told to stay put, he'd get up and start pacing again.
On my last day at that job, the last thing I saw was Marion, pacing in the parking lot, throwing his head back to "laugh." Later I wondered if all along I'd been dealing with a ghost. All these years later, I still don't know.