My two-timing dog, fluffy cheater revealed

After building my straying dog a much larger pen, almost a half acre, he has escaped two mornings in a row! Yesterday (sunday) there was a light coating of snow that revealed his push out spot, but unfortunately was spotty so we couldn't follow a trail. We walked up the road calling for him but couldn't find anything but some paw prints that may have been his, or may have been any other medium sized dog. This morning he was only out for 10 minutes before we went to let him back in and discovered an empty yard. The hunt for my precious mini aussie was on! We drove up the road, with the intent on pulling down any un-gated driveways and knocking on doors. the first two driveways have gates, so our first stop was three houses down and not to far from the suspicious paw prints. My husband is the one to knock on the door, and from inside he hears "It's those people looking for their dog". A man comes to the door and instructs his wife to let the dogs out the back. Now understandably my husband finds this a bit suspicious as we have never met these people. My husband shows him a picture of ralph and says that he is wearing a collar with tags. The man says "ya, its a black collar?". My dog has long hair, and the only way you can really see his collar is by moving his fur out of the way. The man denies ever seeing my dog, but as we are pulling out we see though the trees our little dog trotting across the neighbors yard. So here are the facts: my dog escapes in the morning (only the a.m), he "possibly" goes to this house, the man was very shady, and knew the color of his collar but denies contact with him. What I would like to know is if any of ya'll have ever heard of anything like this and have suggestions on how to make it stop.