A while ago frandowdsofa posted a link to a story about mysterious stone carvings appearing, Onthe BBC news site
appears to explain the mystery, while suggesting that there remain many more to be found as there are supposed to be more than fifty in total.
The related link at One to One Productions is interesting for those who wish to follow the story further.
So, my commiserations to frandowdsofa if one hasn't turned up by now I doubt it's going to happen.
Unfortunately the one to be found on aspodeline's page isn't one of them!