Okay, since I found out there are no any mark on the floor, I can only say one thing - whoever developed it is retarted or haven't tested anything on that event (that's what I guess after 2nd mission bug). Do you really know what events are about? not about making players mad for sure, and that's what you did. The only thing I see on chats now is complaining about 3rd mission retardness.
Do you really think someone would dig EVERY GOD DAMN SQM on that island?
Or this
Or this since the word "nearby" doesn't really tell much which islands
Sorry for calling it retarded, but it is retarded. NOBODY will dig over 5k sqms if not more lol.
That's why I think there should be some hidden X on the sand/snow or w/e, something that will make it possible to do. Try to do it on ur own guys, You'll see that this mission is impossible to do.