He's controlling and manipulative, right? He's the only one of the two who drives, right? And their cell phones are off, or they discarded them, or they are not charged, because they are not pinging on any towers.
He has her right where he wants her - under his control. It's quite possible, even likely, that she is not in a position to call for help nor run away.
He or they will eventually need to surface - for food, gas, and money. I keep saying that. I also keep saying that he's an average-looking guy driving a very typical vehicle. It will take luck and eagle eyes to spot him/them.