The needle-in-a-haystack mission in "Stalker 2: Heart of Chernobyl" is a relatively unique main mission in the game. In the mission, players need to find Eyepatch first (this is an NPC). You will find him hiding in Zali. A windmill east of West Asia. So, head over there when you're ready.
How to find the eye patch in the Needle in a Haystack mission of STALKER 2: Heart of Chernobyl
Eyepatch's hiding place, you will find him hiding in a windmill east of Zalicia. So, head over there when you're ready.
Once you've located the blindfold, follow the orange guide dot until you see the windmill in the distance, then head in that direction. When you come to the outside of the windmill, walk around the windmill until you see the stairs leading inside, then follow the stairs into the interior of the windmill, taking care to avoid triggering traps.
Once inside the windmill, crouch down and begin slowly climbing the winding stairs, keeping an eye out for possible tripwires and shotguns scattered along the stairs. There will also be some canisters on the stairs, and it's almost impossible to avoid them without making a noise, so you can deal with these depending on the situation. Once you reach the top, Eyepatch will greet you with a shotgun pointed at you.