The man in the black leather jacket may have sought shelter from the cold when he climbed into an old shed by the train tracks in Rosemount. He did not come out.

Months later, a railroad worker opened the door and found him there, still dressed in a Wilson's Leather motorcycle jacket, a striped button-down shirt and cargo pants. He was short but thickset, with long brown and gray hair, and wore metal-framed glasses and a hoop earring.

Yet the most unusual thing about him is this: The authorities have no idea who he is.

Just as the living cannot hide from the reach of modern technology, the dead have fewer and fewer ways of ­eluding identification.

Advances in DNA and other biometric analysis, the electronic trail of social media and a concerted national effort to match missing persons reports with unidentified remains have solved mystery after mystery, often within hours, and in some cases, put names to bodies that had been John or Jane Does for years.

Last year, the Minnesota Bureau of Criminal Apprehension appealed for people with missing family members to donate DNA samples, as part of its campaign to identify at least 100 sets of human remains stored at medical examiner's offices around the state.

The National Missing and Unidentified Persons System (NamUs), a publicly accessible national database, currently has 9,862 records of unidentified remains nationwide.

Todd Matthews, communications director for NamUS, suspects the number is closer to the 40,000 estimated by the U.S. Justice Department a decade ago. But Matthews is also seeing cold cases solved so frequently that it has become almost routine.

The database includes 69 records from Minnesota that date back 50 years. Some of them are unlikely ever to come off the list. There's the body of an infant left in a bus station locker in Hennepin County in 1964. A foot was discovered on a Mississippi riverbank in 1969.

Yet for some people, these mysteries inspire a peculiar determination. In August, authorities went to a cemetery in Blue Earth to exhume the remains of an unknown woman, 34 years after she was slain and left in a ditch in ­Faribault County.

The push to create a DNA profile for this Jane Doe came as a result of years of pressure from Deborah Anderson, an IT staffer at Minnesota State University, Mankato who has made the case her mission.

"We can only do what's right for those people," Anderson said. "She doesn't have an advocate. She doesn't have anybody."

It's hard to stay anonymous in close-knit Minnesota, even in death.

Shawn Wilson, investigations supervisor for the Hennepin County medical examiner, said his office buries an unidentified individual about once every three years, and that's becoming even less frequent. Some of the existing cold cases might involve a tiny bone fragment, decades old, with no hope of identification.

Then, "there's still a few that haunt me," Wilson said. One of them: A man with a goatee found dead in a freight train that started in Chicago, rolled through Wisconsin and stopped in Minneapolis in December 2003. Despite a "high potential" for identification, 418 potential identities have already been suggested and ruled out. There is still no name to place on his grave at Crystal Lake Cemetery.

The man found in Rosemount Sept. 29 probably had a similar vagabond existence.

"This guy is unique in the fact that he's not considered a cold case," Wilson said.

Rosemount police believe his death was natural. As the forensic work continues, the police and medical examiner have gone public with what little evidence they have. Some newspapers found with the body indicated that he probably hung around the area from mid-October through mid-December 2013.

He may have bought things at a convenience store in town. At American Legion Post 65, a flier pinned to the bulletin board shows images of the leather jacket, the spectacles, the earring and an empty brown leather knife sheath.

"We wonder if we waited on him, we wonder if he was in here," said post manager Kristy Geraghty. "What bothers me, is no one missing him?"

Behind the American Legion post, and across the street, the ground rises slightly to the railroad tracks. On the other side of the rails is the red-sided shed, barely long enough to lie down, where the man lay undiscovered through a cold winter, spring and summer. The door is now barricaded by a metal shaft.

Contact James Eli Shiffer at james.shiffer@startribune.com or 612-673-4116. Read his blog at startribune.com/fulldisclosure.