Sounds of footsteps return

This occurred just this morning. I was up and ready for the day first. I had already come downstairs and had taken the dogs out. I had put up the screen at the bottom of the stairs so the dogs could not go back upstairs. Sometimes they are a bit difficult to bring back downstairs. My wife taking longer had stayed upstairs. But when she was ready to come downstairs she said she distinctly heard me coming back up the stairs. As the rear stairs are rather narrow and she needs lots of room to navigate them, she said she waited for me to appear. The sounds of someone coming up the stairs ended at the turn in the stairwell. As I did not appear coming around the corner in the stairs; she said, "Are you coming on up or what?" She got no reply and then she heard me talking to the dogs in the kitchen and knew I was not on the stairs. She came on down and told me about the episode. She insisted it sounded exactly like someone coming up the stairs. As the gate was still up when she reached the bottom of the stairs it was rather obvious that neither I nor the dogs were on the stairs. That it was plain enough for my wife to ask whether or not I was ccming on up indicates to me that she heard something, but what?