Taking the article at face value and assuming it is accurate (not always a sensible thing to do with the press) it could be either a souvenir hunter or a larper.
Souvenir hunting has precedents, the King Stone at the Rollrights is now shaped that way because people kept removing bits of it and Stonehenge also used to get bits chipped off when the stones were open access.
The larper angle usally occurs because somebody thinks owning a piece of an ancient site or an ancient artifact will give them some kind of special advantage - it won't, it just vandalises the site.
Something is not right. This message is just to keep things from messing up down the road