YAPHANK, N.Y. (AP) _ The play ''Oliver'' was the clue that enabled FBI agents to find an 11- year-old Kentucky youngster who had been kidnapped nine years ago by his father, authorities said.

George Wells was reunited Friday with his mother, Lou Ellen Blackwell, 32, at Suffolk County police headquarters.

''It was the most touching thing I have ever seen in my life,'' said Lt. Stephen Steidel, commander of the Juvenile Service Unit. ''I don't think there was a dry eye in the stationhouse.''

The boy and his mother boarded a flight Friday night for Burlington, Ky.

The father, Curtis Wells, 36, of Ridge, N.Y., was charged with unlawful flight to avoid prosecution, said FBI spokesman Joseph Valiquette.

Steidel said there was no evidence the boy had been abused and that he looked very healthy.

Wells, of Ridge, was indicted on the charge of parental kidnapping in Covington, Ky. in October, said Valiquette.

He abducted his son and daughter, Emma, in September 1975 shortly after his wife was awarded custody of the children in a divorce settlement, said Steidel. Six months later, Emma was returned to her mother, but the boy's whereabouts remained a mystery.

Mrs. Blackwell kept after police and hired private detectives, but she never lost hope. She remarried, had two other children, and continued searching for George.

Two years ago, her spirits lifted when her ex-husband, ''perhaps out of compassion,'' mailed her a recent photograph of the boy whom she had not seen since he was 21/2 years old, Steidel said.

Mrs. Blackwell gave the photograph to the National Center for Missing and Exploited Children. George saw the picture while watching television with a babysitter, who called his mother and told her ''her boy was OK, not to worry,'' said Steidel.

She would not tell Mrs. Blackwell where he was, however.

Later in the day, George picked up the phone and called his mother, said Steidel.He told her he was on Long Island but was not more specific. He talked with her for awhile, and mentioned the school play, ''Oliver,'' in which he starred recently.

FBI agents combed school after school on Long Island until they came up with the elementary school which had recently produced the play, adapted from Charles Dickens' novel of an orphan boy.

Suffolk County Family Court on Friday gave Mrs. Blackwell permission to take her boy, who was picked up at his school and brought to police headquarters to join his mother.