A 9-year-old girl disappeared near Dayton while walking her dog to a neighborhood park near her home 25 years ago. A successful Ohio State University medical student vanished from a campus-area bar in April 2006 and didn't show up two days later to board a plane for a spring break trip with his girlfriend. A 4-year-old boy, carrying a red toy fire truck, went missing without a trace after playing with friends in a small northeast Ohio town nearly 100 years ago. These are just some of Ohio's missing persons cases that remain unsolved. They represent children, siblings, parents,...