US Assistant Secretary of State for Public Affairs Philip J. Crowley had confirmed during a press briefing this week that it "was US Embassy staff driving the car that allegedly hit the civilian.
On Friday, the Lahore High Court ordered provincial authorities to impound the vehicle and arrest the accused involved in Rehman's death.
But the car driver as well another US official involved in the incident are no more in Pakistan, in fact they are back on American soil, ABC News quoted the US official, as saying.
Davis is accused of gunning down two Pakistani men, allegedly in self-defence during a "botched robbery."
American officials said that the driver of the vehicle held the same diplomatic visa as Davis.
Authorities in the Punjab province have said that they sent five letters to the US Embassy, asking it to hand over the driver and that vehicle, but have received no response so far.
It is unclear when the driver and his passenger were spirited out of Pakistan, but a senior US official said that it happened soon after the shooting incident.
Meanwhile, Davis is in a high-security detention centre in Lahore and is expected to stay there until a court hearing next month, despite repeated demands by the US to release him immediately on the grounds of diplomatic immunity. (ANI)