RU version has different hint text then any other language. It says something like (with help of Google translator):
"Damn natives chasing me third day in desert. My horse died yesterday, every step is harder and harder. I tried to ask for protection in Pilgrim's Sanctum: Sincerity, but they are afraid of the natives. I must bury everything valuable here and pick it up later. I'll try to ask for help in Pilgrim's Sanctum: Sharing."

https://gyazo.com/4b69c482ce86becac0e6bf3cab235ea5

https://gyazo.com/0a2343f668311762613c5f22d1d03c58

Position yourself between the two bone piles with the mob on your right.https://imgur.com/a/5UeMUpt

dont get distraced from all the useless comments here!

you will get the questitem from a bottle with a note you can randomly obtain whilst fishing on the coast of Kamasylvia, Drieghan or when harpoon fishing! (i got mine after ~10hrs afk fishing at the coast of drieghan)

you can set up a twink fishing there, if the bottle drops, use it to get the questitem, accept the quest and do it with you mainchar.
if you need help finding the spots to dig, follow the guide from blackdesertfoundry

good luck