It was nothing short of a miracle when a lost dog was reunited with its owners after a marathon 31-hour trek across four major A roads and miles of treacherous moorland. A family who had given up their whippet-terrier cross Jack for dead looked outside to find him asleep on their doorstep. Exhausted and sore-pawed, the pet dog had walked 15 miles along an unfamiliar route - crossing a four-lane bypass and one of the country's busiest motorways. What makes the feat even more amazing is that it suffers from a fear of traffic, and walks with a limp, after being knocked down by a lorry five years ago. "He had been missing for a day-and-a-half and we'd all but given up. We'd had dozens of friends and neighbours out looking for him but decided to call off the search. On a whim, I had one more look outside the back of the house just in case he had returned. I glanced down through the window of the door and did a double take, because there he was," The Telegraph quoted David Cooper, 46, as saying. "He looked up at me, and his eyes said: ''Have I been naughty?'' The children smothered him in hugs for the next hour, so I think he knew he was forgiven," he added. Jack had become separated from Mr Cooper, an accountant, and his vet wife Liz around 2pm Sunday May 16, while the couple were walking in Dearne Valley Park to the east of Barnsley town centre in South Yorkshire. "We really have no idea how he got across. There are a couple of pedestrian subways, but he would have no idea where they were so it's possible he just made a dash across the traffic," Cooper said. The Coopers subsequently learned that he was seen walking along a main road in the village of Oxspring around 24 hours later, having traversed miles of rough moorland and woods. "I've asked all my colleagues at work if they can tell me how dogs can navigate when they've never been somewhere before, but they're just as baffled as me. Everyone thinks it's quite amazing. We bandaged his legs but he's out walking again now, although he is staying a little closer," Cooper added.