Yeah this has happened to me a fair bit actually. I've got this one spot on my kitchen windowsill where a little ceramic pot keeps ending up shifted about 10cm to the left, and I live alone so its not like someones moving it on me. Happened maybe 6 or 7 times over the last year, always the same object, always the same direction.
Tried to logic my way out of it - vibrations from traffic, uneven surface, whatever. But the surface is dead flat and nothing else on the sill moves.
What gets me is the repetition. A one-off you can write off but when its the same spot over and over it starts to feel like something is making a point. Anyone else noticed a pattern like that or is it always random objects in random places for you lot?