Why would bored teenagers circle the stone in white paint? At least, that is to say, they don't sound like the kind of bored teenagers that usually hang round street corners smoking and drinking cans of white lightning. 'What shall we do tonight?' ' Oh I thought we might go up to that weird stone with this can of paint.'

So whoever it was drew round the stone / carving, not actually painted the design in (which you'd think'd be more tempting for a mere teenage vandal who happened to have some paint with them)?

Maybe they were doing a bit of health and safety, outlining it as a trip hazard. NO NO NO that's far too flippant. I'll get my coat. Let's go and lynch the culprit.