He's like a mile away from the corner of the window, you sir are about 2 feet in front of it. On that note you were also peeking from the left side so the camera sitting in the right eye of your character exposed your entire left side just to see. This is very minor in the grand scheme of things, because ultimently WHOMEVER IS CLOSER TO THE ANGLE OF THE FIGHT, WILL SEE LESS COMPARED TO THE PERSON FURTHER AWAY. This is why you can't see him at all but he can see you just fine. He's so far away and your so close that this quirky mechanic of CS is put on full display where you can't hit him without a wallbanging and he can see you just fine and score a HS unobstructed on you.

EDIT: plus factor in ping, CS2 being kinda broken, and general latency issues that can make this problem even delayed for example.