FWIW... eight years ago, I adopted an escape artist from a local shelter. I was told that he was surrendered because he was always finding new ways to get out of the house and yard. So, I knew this when I adopted him and he did not disappoint. He scaled my six foot fence the first day I let him out into the yard. A few days later, he figured out how to unlatch the gates. He took advantage of anyone new entering the house and would slip between their legs. He dug holes under the fence and squeezed his way out in a matter of minutes. He backed/slipped out of his collar and ran off in a park with me chasing after him. If you have never had a dog like this you cannot know how terrifying it is to chase one back and forth across a street and around a neighborhood until he finally, eventually stops. Now, he has become a wonderful, well behaved companion but I had to change a few things in my environment to make it more secure. My gates now have locks, there is fencing that he cannot dig under and I key locked my front door so that visitors must ask me to open it. I walk him on a harness he can't get out of. It helps that he is a lot older now. He doesn’t really try to do the things he did when he was younger. Sometimes dogs just get out of their home or fenced yard. Sometimes they do unexpected things. Your dog may never have dug a hole under your fence and then one day out of the blue he does. He may never have tested a gate before and then one day he does for some reason. Secure the environment for them. Make sure they have a collar on and make sure they have a microchip in case they get out of the collar. Usually there will be a happy ending and they will find their way back to you. Glad this was the case here!!