Cat on the stairs

I thought I had posted this two weeks ago when it happened. The post must not have been completed. I will retell tell the event as best as I can remember it. It occured at the foot of the rear stairs, just off the downstairs bathroom and kitchen. The dog gate was up to keep our two schnauzers downstairs during the day. The weather was cloudy outside and cold.  The kitchen light was on which gives some reflected light to the bottom few stairs of the rear stairway. The rearstairs light was not on. As I walked from the diningroom toward the kitchen movement on the stairside of the dog gate caught my eye. I saw a black cat move across the bottom step, turn and go up the stairs fading in the darkened hallway. At first I thought a stray cat had somehow gotten into the house. Then I thought of my dogs who were totally unaware of it. A cat in the house would have had them going berserkl. But to be sure I opened the gate and went upstairs, seeing nothing in the way of a cat. Both dogs followed me and bounded on upstairs as they are wont to do. If there was a cat anywhere upstairs the dogs were not aware of it; which I find hard to believe. Checking out the upstairs is not that difficult in winter as we typically keep all doors off the main hall shut except the master bedroom and the bathroom. Even the hallway to the frontstairs is closed off. So any cat in the upstairs would be isolated to the hallway, bathroom and master bedroom. Quickly checking those out it was acertained that no cat existed there. Calling my dogs who were busy romping around the hall and rooms, we went back downstairs and I had to chalk up the incident to another strange sight in this old house.