I DROPPED MY PHONE ON A THING THAT LOOKS LIKE A DRAINAGE?

So i was looking for something and in my other hand was my phone and i accidentaly dropped it inside it. HOW DO I GET IT BACK????? i tried calling it but its on silent mode. Its like a rain drainage attached to your house vertically and when you look down theres like this hole? i cant see it but i think its not deep at all, and its not wet. dry leaves, dry pipe and stuff. PLEASE??