Thanks for the information about Amtrak.
One case that came to mind was of a (formerly) pet case of mine - Pat Collins, a missing graduate student. They determined that he had called up Amtrak reservations but never made one, and many decades passed without much progress. It turned out he had taken Amtrak to a remote location in New York State and killed himself; his remains were only recently identified. Besides the proximity to Amtrak, his father on Live PD tonight mentioned that he didn't take his large backpack with him - and Collins was found with a "ditty bag" which is a small backpack and contained basically enough to get him to his destination, and the drugs he used to kill himself.