Where oh Where can he be

So last night I was shopping with my friend mel-shel. Her fire-alarm phone started to go off. It was Jason telling me that he couldn't find Max. He had let him go outside to go potty. Background: Max is a wimp of a dog. He does not like the snow. When we let him outside in the winter he goes to the bottom of the stairs and does his duty. When he is done he immediately runs upstairs and scratches on the door. So now back to the story. I came home about 1 hour later. Max still was no where to be found. We spent hours driving up and down the street, calling his name. Still no max. We worried about him all night long. We woke up and called all of the shelters to see if they had a dog turned in. No one. At 1:30 this afternoon I was on the computer checking my mail. I heard...thump thump thump. I ran to the door and there was MAX!! He was standing at the back door. I hurried and opened it expecting him to be hurt or wet. Nothing. He didn't even need to eat and he was WARM!! We still have no idea where he came from. There were no tracks in the snow...nothing. So the mystery remains. Where or where has my little dog gone????