I was there last Saturday and noticed a similar patch of chipping damage on the opposite side of Long Meg. Dunno if it was done at the same time or since...?

Someone must go up there quite often - every time I visit there are new 'offerings'. Decaying fruit, crystals, feathers, symbols on paper blowing about etc.
And clay masks.
And a potted conifer this time.

I expect next time I'm there I'll have to climb over a white picket fence and tip-toe across the herbaceous border.