FBI spokeswoman Rebecca Wu said the responding officer reported that Maier was unharmed, but seemed tired. As the hours since her disappearance passed, investigators had feared the worst.
"The chances are not as good as time goes on when a child is abducted," Wu told ABCNews.com. "You always hope for the best."
After 26 hours, Alisa's parents rushed to the scene two hours south of the town of Louisiana, Mo., where the girl was abducted. There was a tearful reunion with her at a police station before Alisa was taken to the hospital.
She has been able to provide more information about her abductor, a white man in his 30s. But authorities were still unsure where she was or what happened to her since she was kidnapped from her front yard.
"The family wanted to convey how grateful they were for the community response," Wiehle said. "This was a very happy ending."
The most noticeable thing about the abductor's car was its noisy muffler.
"The car had such a loud muffler that it caught attention of people and that's how they noticed the child," Wu said.
Monday's kidnapping triggered a massive search and an Amber Alert for the car that sped off with the little girl as her mother made a desperate, but futile attempt to catch up.
Alisa was grabbed while playing with her older brother outside the family home on South Carolina Street.
Alisa's mother "got in her van and took off up the road in the direction that her son pointed but the car got away," neighbor Anita Mcklevis told ABCNews.com.
Her brother told police that a black four-door car, probably a convertible with tinted windows, pulled up to the house and a thin man made off with the Alisa.
Police met with the FBI to discuss the case as volunteers went door-to-door with fliers, asking for help from anyone who may have seen Alisa.
Police were examining surveillance video from local businesses in hopes of finding some clues in the case.
The town is near a bridge that crosses the Mississippi River into Illinois and law enforcement officers from both states were involved in the search.
Mcklevis said her son was standing outside a friend's house near the place of the abduction and saw a dark car circling the neighborhood for hours before Alisa went missing.
"He didn't pay too much attention and went inside the house," she said.
"When my son came back out, he said Alisa's brother was saying that a young man who looked to be in his early 20s had grabbed his sister and taken her away," Mcklevis said.
Mcklevis described the town of Louisiana, located 75 miles north of St. Louis, as a quiet, safe place.
"We were up all night just thinking about this," she said. "This is kind of town where you don't have lock your doors. You know everybody. The kids play outside all the time."
Alisa's brother described the alleged abductor as a thin white male, possibly in his late teens or 20s with dark, curly hair. He was driving a black or dark-colored four-door sedan with possible front end damage, according to authorities.
"These kinds of things don't usually happen around here," Mcklevis said.
Anyone with information can call the Louisiana Police Department at (314) 754-4021 or the Pike County Sheriff's Department at (573) 324 3202.