Four-year-old Denise Gravely, who disappeared here 19 months ago, was found unharmed in upstate New York.

Denise, who was 2 when she disappeared from her front yard, was the subject of a lengthy search that culminated Thursday when Cleveland police were informed that she might be in Mayville, N.Y.

Denise was reunited with her mother, Patricia Thompson, last night. "I'm numb . . . overwhelmed," said Thompson, who has remarried since her daughter's disappearance.

Thompson was alerted to the possible finding of her daughter on Thursday, and she accompanied law enforcement officials to New York.

Joseph Griffin, special agent in charge of the Cleveland FBI office, said the Mayville home, in a middle-class neighborhood, was watched about 90 minutes before a man and woman left with the child and were confronted by agents. The couple was not held, but their 21-year-old son was arrested in Cleveland.

"There are some indications that this was a child sale, but we can say no more than that right now," Griffin said. "From all indications, there was no mistreatment of the child."

Denise was reported missing Aug. 28, 1980. Just before New Years Day, 1981, her father, Earl Gravely, died of carbon monoxide poisoning from exhaust fumes in a rented garage near the home. The coroner ruled his death as a probable accident.