If your pet gets out of the yard and runs off, the very first thing to do is to go and look for them right away. There is a great chance that they will be hit by a car, or even picked up by someone passing by that sees them; so the sooner you are out there looking, the better the chances of getting them back will be.
Some dogs are escape dogs, and will look for a place to get out of the fence. I had a Pekinese that would literally go along the fence with her nose right up to it, looking for some kind of a hidden hole in the fence (usually buried in think bushes), and then she would wiggl through it to get out. Fortunately, she also had a good sense of "home", so she never wandered far, and always knew how to get back home again. Then, she would stand outside of the gate and bark for me to come and let her in; which was usually my clue that Red had found another escape hole somewhere in the fence.
Then, I had to spy on her, and see where she was getting out, so I could patch the hole.
Most dogs are not good at finding their way back home, and once they are out that gate, they are running, and then totally lost. If you can't find them right away, calling the dog pound and checking with veterinary offices is a good thing to do next.
