NEW YORK (AP) — Authorities say a family caravanning with a woman and her toddler in Florida took the 3-year-old to New York after the boy’s mother was arrested on fraud charges, abandoning him at St. Patrick’s Cathedral with a note stuffed into his hand bearing the name of a detective working the case and the words ‘‘call immediately.’’

Eleanor Black, 29, was identified through surveillance footage at the cathedral, police said Wednesday. She and William Scott, 32, were believed to have been the last two people with Nathaniel Fons, and they were also suspected of being involved in the counterfeiting operation in Florida where his mother was charged.

Police said Black came to the famed cathedral on Manhattan’s Fifth Avenue at about 6:30 p.m. Tuesday. She asked at the information desk to see a priest and was told to go around the corner and someone would come down, police said.

She walked out of the building, and a few moments later, Nathaniel walked back in, alone, clutching the note that also had his birthday, according to the security guards who found him. One guard raced out the door to find her, but she was long gone. Nathaniel, however, didn’t seem upset, the guards said.

‘‘He was clean, dressed in shirt, shorts, some sandals. Very calm. … He seemed like a regular kid,’’ said guard Roberto Plumey.

Plumey said he talked to the boy about his favorite colors and cartoons until police showed up.

Nathaniel was in the custody of child services officials in New York. His grandfather, Donald Fons, said from his Land O Lakes home near Tampa, Fla., that he didn’t know when Nathaniel would return.

‘‘They said he’s fine. He’s happy,’’ Fons said. ‘‘He is happy and he is in good health.’’

‘‘It’s just phenomenal. It’s been a roller coaster for the last three days,’’ Fons said.

Flagler County authorities in Florida had issued a missing child alert for Nathaniel on Sunday, after his mother was arrested on charges of operating a counterfeit money operation. A convenience store clerk reported receiving a counterfeit $100 bill and gave authorities a description of the recreational vehicle the suspects were driving, Flagler County Sheriff’s officials said.

Authorities stopped the RV, reported stolen out of New York, and arrested Nathaniel’s mother Erin Comeau, 26, on charges of grand theft auto and organized fraud. Another person in the RV, Christopher Brandstter-Howell, 21, was arrested on a charge of possession of a controlled substance.

Comeau told officials her son was in a separate car traveling with Black, Scott and their children. Black and Scott are suspects in the counterfeit operation. Their abandoned Chevy Suburban was found by Jacksonville sheriff’s officials in a hotel parking lot.

Comeau said in a statement to Flagler County authorities that if she was to be jailed for a long time, she wanted the boy to be placed in the care of his grandparents, Donald and Frieda Fons, but only temporarily.

‘‘I do expect my child to be returned to me when I am released. I am not signing over my rights to permanently lose my son,’’ she wrote.

Donald Fons said he hoped the boy would be released to his grandparents after a hearing in New York. He wasn’t sure when the hearing would take place.

Fons said the boy, nicknamed Nathan, lived with his parents at his grandparents’ home from birth until last June, when Nathan’s father took a job on a fishing boat in Vancouver, Wash., and the couple moved to Washington state. But his father was arrested on probation violation charges and was returned to Florida, Fons said. He is still in jail.

Fons, 57, a former Denver sheriff’s deputy, and his wife said they started proceedings to adopt the boy four months ago. He said that’s when Comeau took off with her son, traveling around the country. She’d post updates and photos on Facebook, but they could never find her.

‘‘The range of emotions have been from breaking out crying to just joy,’’ Fons said. ‘‘I’m just going to give him a hellacious hug and just show him that someone loves him. We’re just planning to spend as much time as possible with him and get him acclimated into our family again.’’