Then they are still rocks on a mountainside - just look a but different.
I you went up a mountain tomorrow and carved a face in to a rock and then left it there but then someone came along after you and took it - could you prosecute them for stealing??

Not really.

But if you could produce evidence that your carvings are worth money and belonged to you - then you could maybe prosecute.

But if you rock up in court with no evidence of how much they are worth etc...you prolly aint going to get very far!