Ghost at Home?

I have been wanting to blog about this for the longest time (since I discovered it at least), and it's just now that I'm thinking that maybe, there really is a ghost in our condo. Ok, I know, I'm just scaring myself, but how do you explain the fact that whenever I take a bath, and I completely turn off the heater and the faucet, the next day, the lever of the faucet is up (when it should be down!). My helpers confirmed that they never used my bathroom and that they even get water from the other bathroom whenever they clean ours. I talked to my colleague about this and he explained that it's because of the water pressure that's trapped in the tubes of the heater. So the lever goes up and some of the water leak (which "explains" the wet floors). Whatever, I still get so spooked out because of this. Why? because how can you explain the change of setting of the showerhead?