The girl and police said she managed to escape her captors as they directed her to attack a paramilitary checkpoint in northwest Pakistan.
Sohana Jawed, who is in third grade, said she was abducted near her home in the northwestern city of Peshawar on Saturday and taken to Lower Dir district, a four-hour drive away, where she was found on Monday.
Police in Lower Dir presented Jawed at a news conference, where she told her story dressed in her blue and white school uniform. But police in Peshawar said they haven't received a complaint of a missing girl and haven't identified a resident with her name.
Initial police reports of security incidents in Pakistan are sometimes wrong.
Militants in the country have often used young boys to carry out attacks, but the use of young girls is rare.
Jawed said during the news conference that she was grabbed by two women while on her way to school and forced into a car carrying two men.
One of the kidnappers put a handkerchief over her mouth that knocked her unconscious, Jawed said in a separate interview with a local TV station.
When she woke up and started crying, one of the women gave her cookies laced with something that again knocked her out, Jawed said. The next time she woke up she found herself in a strange home, she said.
"This morning, the women and men forced me to put on the heavy jacket and put me in the car again," said Jawed.
The suicide vest contained nearly 9kg of explosives and seemed to be designed to be set off remotely, Lower Dir police chief Salim Marwat told The Associated Press.
"Most likely it had to be detonated through a remote control since a minor was wearing it," he said.
The kidnappers brought her to a checkpoint run by the paramilitary Frontier Corps located about 10km outside Timergarah, the main town in Lower Dir district. When they got out of the car, she sprinted toward the paramilitary soldiers to show them what she was wearing, said Marwat.
"I got the chance to release my hand from the woman and run," said Jawed.
By the time the paramilitary soldiers realised what was happening, the kidnappers had escaped, said Marwat. Police have launched a search operation to find them, he said.
It's unclear why the kidnappers didn't detonate the suicide bomb vest after Jawed ran away. Marwat suggested they may have simply panicked and fled.
Asif Khan, the police chief in the area of Peshawar where Jawed said she lived and was kidnapped, Hashtnagri, said they haven't received a complaint of a missing girl and haven't identified a resident with her name.
Police in Lower Dir plan to ask Jawed additional questions after she is examined by a psychiatrist, who is helping her cope with the trauma of her ordeal.
"Police will try to get more information from her once she gets normalised," said Marwat.
