OK well I will share another story with you all that happened fairly recently (True).
My daughter was 15 months at the time and is a bum shuffler as opposed to a crawler. Hubby and I were putting a brand new clock up in her new bedroom as we had not long moved her out of the nursery.
Shae was in the passage and playing happily, hubby was in the room with me. Next thing she lets out this terrified scream and bum hops as fast as she can towards the bedroom door. She stops and looks behind her, screams again (crying by now) and races towards the door where I scoop her up.
Trying to calm her down I walk through the back passage to show her everything was ok and I felt something brush past me. Shae didn't settle until I took her outside where we spent the rest of the afternoon.
That night there was someone walking through the house ... its all boarded so you can tell the difference between footsteps and just the general popping of the house as it shifts and settles. Even hubby heard it and went to look.
Nothing!