Go to the part of the movie where they are all going to save the grandmother. You see the dog run away. They do not take it in to the car with them when they are escaping. If you are saying well maybe you couldn't see the dog go further in the movie. When they are in the boat going across the acid the dog is not with them there either. If you go even further in the movie you will see that the dog is in the car with them safely sitting in the back seat. He is also saved at the end in the tunnel.