Perhaps it wouldn't hurt for the land owner to know that the other people are aware that the stone has fallen.
The temptation for him/her might be to move it quickly and get the track cleared. The obvious way of doing this would be a JCB. I'm told that JCBs, when used carelessly, can cause a bit of damage to stones (Iron Age earthworks, or anything else that gets in their way).
Kammer x