New York (CNN) -- A 13-year-old teenager with Asperger's syndrome spent 11 days in October wandering New York's vast subway system until a police officer recognized him from a missing persons' poster, according to police and the youth's mother.

Francisco Hernandez Jr., who has Asperger's, a developmental disorder that affects the ability to socialize and communicate, disappeared on October 15, after he thought he was in trouble at school, according to his mother, Marsiela Garcia of Brooklyn.

Garcia told CNN that she contacted police when her son went missing, but received little help.

Garcia said she and her husband took matters into their own hands and posted signs and fliers around the neighborhood, in public areas, even in the subway. "Nobody told me nothing," she said.

The teen was eventually identified by a transit police officer in the Coney Island section of New York, after the officer recognized him from the fliers that had been posted throughout the subway system. He was returned home unharmed.

Garcia said her son wore the same clothes for 11 days, slept in subway cars, used bathrooms in stations and spent most of his time over those days underground. He had $11 when he disappeared, she said, and he ate lollipops, potato chips and other food he bought in subway stations.

"He's never explained (to) me what happened in these days," Garcia said.

Francisco told his mother he didn't ask for help or communicate with anyone, which experts say is not uncommon for people with Asperger's syndrome.

The New York City Police Department originally treated her son's case as that of a runaway, Garcia said. After five days, the police department's missing persons unit paid her a visit and gave her advice on where to look, she said.

Garcia, 38, a housekeeper who came to the United States from Mexico 16 years ago, said she became so frustrated that she turned to the Mexican consulate in New York for help, and she said the consulate again contacted police.

The youth spoke briefly to CNN, saying that a transit officer approached him and asked whether he was the boy on the missing persons posters. "I just said that I'm Francisco and that's it. I just went with him," the teen said.

New York Police Commissioner Ray Kelly was asked about police actions in the case on Tuesday, during a news conference on other, unrelated subjects. He said police "waited for a few days, because obviously (the missing persons unit) would be overwhelmed if we took every report of a young teenager not home."

Kelly said proper protocol was followed.

"I believe that all appropriate action was taken to find this young man," Kelly told reporters.

CNN's Mary Snow and Shirley Zilberstein contributed to this report.