Cobblestones

Every night I mark the cobblestones with chalk.
When I wake up, the markings are scattered around the street.
Does someone wipe off the markings and add them in new places or shuffles around the stones?
I tried to set up a video camera, but it’s far too dark. No streetlamp.
I’ve also tried to sit on the steps and watch the street, but I can’t stay up as late as I used to. I fall asleep on the steps.
I wake up, and the chalk marks are gone.
And then, I see myself in the mirror… they’re on me.