Quick answer
Direct verified-existence answer, explicit unknown location/reward state, and an observation log without fake coordinates.
Start here when this is the exact player task you searched for. The sections below turn the question into steps, checks, and next pages.
Buried chests are named officially, but their exact position, timing, and rewards were not confirmed. Record the visible area, depth, time, reward text, and whether the observation repeats before treating it as stable.