Bianca Jones was driving with her father Deandre Lane, 32, near their Detroit, MI home, when a man with a gun held him up and drove off in his silver Mercury Grand Marquis on Friday.
The alleged hijacker apparently hadn't noticed the child buckled into her car seat, but the car was recovered 10 minutes later, less than a mile away.
But the little girl was gone.
Police Chief Ralph Godbee, however said that the story from ex-con Lane, who is currently in custody on unrelated charges, remains in question.
He told the Free Press that they: "Will not comment on the quantity nor the quality of any evidence or information we have gathered to date.
"However, in the interest of allaying some of the fears of the public regarding the apparent randomness of Bianca's disappearance, the authenticity and credibility of the original version of events is under intense scrutiny by our investigative team."
A reward for information that leads to the child's return was increased to $17,500 after an anonymous donor contributed $15,000.
Godbee added the search remains "priority one."
Detroit police, along with the FBI, Michigan State Police, Wayne County Sheriff's Office and several community groups are scouring the city for the little girl.