I have a mild interest in these kind of cases and for some reason one in particular always stick in my memory. The Johnny Gosch case, or "Why Johnny can't come home".
Johnny Gosch, a paper boy in Iowa who disappeared and presumed to be kidnapped on the morning of September 5, 1982. He had been missing for 38 years.
A few months after his disappearance, there was a report of a young boy claiming he's Johnny and screaming for help in Oklahoma before being dragged away by two unknown man. Even though it was never confirmed, the mother believed it was her son. The trail ran cold for another 15 years.
March 1997, according to Noreen Gosch, Johnny's mother, she claimed she was visited by two man, one of them was Johnny, now a 27 years old man. Noreen was confident it was her son due to recognize the birthmark on his chest. She claimed that he didn't say where he is living or where he was going, instead telling her that he had been the victim of a pedophile organization but had escaped and now feared for his life. Johnny and the man left, and Noreen never heard from her son again after that. Whether it was really Johnny or some very well researched cruel joke, or even Noreen delirium and imagined the whole thing, no one can tell.
In 2000, Noreen published a book titled "Why Johnny Can't Come Home", detailing the case and her son visit, as well as condemned the slow reaction of the authorities, as Johnny cannot be declared missing until at least 72 hours passed.
On September 1, 2006, Noreen found photographs left at her front door, some of which she posted on her website. One color photo shows three boys bound and gagged. A black and white photo show someone she claimed to be a young Johnny also bound and gagged, with a brand on his shoulder. She notified the authorities. On September 13, an anonymous letter arrived claimed that it was a reprehensible joke, and that the photo in question is not of her son, but three boys in Tampa, Florida about 1979–80, challenging each other to an escape contest. There was an investigation concerning that picture, made by the Hillsborough County (FL) Sheriff's Office. No charges were filed, and no wrongdoing was established. The lead detective on the case was Nelson Zalva, and he confirmed that the letter was telling the truth. The kids were interview, and there was no evidence of coercing. However, while the three to be in the color picture were identified, the one thought to be Johnny were not. Noreen still believed it was her son. More pictures would arrived, some of them proved to be elaborated fakes from horror movies, while some of them were still unidentified. I believe Noreen continues to post them on her website in hope someone with new information would come forward. The case remains open until today, but considered cold.