Trooper Darren Wright says another trooper was dispatched to check on the car Monday afternoon because it had a sign in the window that said "call for help."
The trooper found the woman in the trunk who said she had climbed in to keep warm after she ran out of gas.
Wright says troopers are confident she wasn't there for three days. The car was noticed right next to the busy highway.
Wright says the car was towed, and troopers made sure the woman was OK and gave her a ride to Leavenworth.