Seen? no.
Heard yes. My gf and I went out to see a movie a few months ago and decided to leave a digital voice recorder on the stairs inside of my mothers house. We were house sitting at the time. I plopped the device right in the middle of the stair case, and we walked out the door. No one else home, and it was about 10 pm. I beeped the horn of my truck so that I knew on the recorder that we had left the driveway.
We came back almost 3 hours later, the dvr was still recording, so I hooked it up to my PC and copied it. I sat there listening to my pc, while my gf put on headphones and listened to the DVR. Within 15 minutes we started hearing footsteps in the house. Some were near the stairs, while others were upstairs (I know the house well enough to know the difference).
A little bit into the recording one of the door handles in inside of the house started turning (you can hear it plain as day) and the door swung open, and then closed again. The doors inside the house make a distinctive sound. They are a hollow wood, probably about 50 years old, and I have NEVER heard any one else's house sound like them.
This wasn't the first thing in that house I have experienced though, I have woken up to someone screaming my name, just to jump out of bed toss on some PJ bottoms and check out each room. No one home but me. (I was living there at the time). I also heard someone walk down the stairs inside (same stairs I put the DVR on) so i wipped my head over to see who it was...no one. I got up, everyone was still in bed. I heard each stair on the case make its distinctive sound as if someone were putting pressure on them one at a time.
Its a fun house sometimes. I enjoy creepy stuff.