The detectives knew who abducted 5-year-old Richard Wayne Landers Jr. in 1994.
His paternal grandparents, reportedly angry about a custody case involving the small boy, took him and disappeared from Indiana.
For 19 years, Indiana State Police searched for him, but it was last October when the missing boy case turned into one of changed identities.
According to a news release on the state police website, a detective was given Landers' Social Security card. He matched it to a 24-year-old man in central Minnesota about 100 miles from Minneapolis.
Police looked at the man's driver's license photo. It could be him, they thought, comparing it to the photo of Landers as a boy.
Some months of detective work followed and police found the grandparents, who they say admitted to assuming new names, in a town near Landers, who has been living under a name given to him by his grandparents.
Landers is married with a child on the way. It is unclear when he will be reunited with his mother, Lisa Harter, and her husband.
Charges in Indiana against the grandparents were dropped in 2008.
A spokesman with the Indiana State Police said the FBI and Social Security Administration also were investigating the case.