RCMP said Tuesday that a person in a rural home south of Grande Prairie found baby Addison sitting in a car seat on the front porch.
The temperature was -24 C with the windchill when the child was taken.
Police said it appeared the child was not injured, but she was taken to hospital as a precaution.
"It's obviously very cold right now in Grande Prairie," said Cpl. Roy Kennedy. "This could have turned out a lot worse if that person hadn't come out of their house."
RCMP said three people have been arrested after a police helicopter found the stolen truck at a forestry mill south of the city.
Officers chased the suspects on foot before taking them into custody.
Kennedy said he didn't know if the person who found the girl was alerted by a doorbell or why they opened the door.
He said he didn't known how long the child was outside.
"We're very happy the child was located, but we're still very much actively investigating."
The light-brown 2010 Dodge Ram was reported stolen in Grande Prairie around 1 p.m. MST.
Police said the truck was taken from outside a home in the Royal Oaks area.
Kennedy said it appears the driver had left the truck running with the child inside.