Tom Swift and His House on Wheels by Victor Appleton

There were two theories to account for the taking away of the House on Wheels. These at once occurred to Tom Swift and Ned Newton as they stood in the rain and darkness near the auto, hardly able to believe their good luck which had brought them to the machine within half an hour of the theft.

One explanation was that the legal authorities of the place -- state police or local traffic officers -- had come upon the parked House while Tom and Ned were in the deserted mansion. Seeing no one in the big auto, but observing that the lights were on, the authorities might have concluded that there had been an accident or that the car was abandoned and so had decided to drive it some place where it could be held pending an investigation.