Sanatorium Specter

I was on a half-night stay at Waverly Hills Sanatorium in Louisville,Kentucky with my fiancee,when I saw what appeared to be a human form standing near one of the doorways in the third floor hallway. I asked my fiancee if she saw it, and she responded that she did. My first thought was that it was another member of our tour group, but then I remembered that every other member of our group was behind us, on the opposite end of the building. I said "Hello,is that someone standing there?", no response. I started to walk closer to the form,it didn't move. I thought I have to be sure, so I'm going to shine my light to see if it is. I hit the light on my flashlight, and the form dissipated into thin air. I started to walk quickly to make sure no one was there, but found no evidence of anyone being on that end of the floor with us. Every other group memeber was accounted for.

I still can't fully understand what it was I saw that night.