The research found that “human hands are remarkably sensitive, detecting the presence of buried objects by perceiving minute displacements in the sand surrounding them”.

It’s literally just touch. It’s the same as how a person silently entering a room makes a not-sound by disturbing the ambiance, or like splashing paint on an invisible person. You don’t need to observe something directly to perceive how it affects other things.

This really isn’t “remote.” We can detect the increased pressure from sand compacting against the object. It’s just touch.