A bearded cyclist jumped into a white Ford Fiesta left unattended with its engine running, before driving off with the shocked owner just metres away.
The man was riding a bike at around 5.50am on Saturday, September 3, on Wimborn Avenue in Grimsby when he stole the car.
The owner had left her car to warm up when the cyclist got behind the wheel, driving it in the direction of Winston Avenue and Littlefield Lane.
The car was found abandoned on Sunday in a parking area off Elder View.
Humberside Police are warning motorists not to leave their vehicles as tempting targets for thieves.
Anyone with information about the incident is asked to call 101, quoting crime reference number 2211707.
Alternatively, call the independent charity Crimestoppers on 0800 555111.