Why won't the police find my iPhone?

Today, my iPhone was stolen in the changeroom in gym from my bag(at school). I had the app find my iPhone and i used my moms phone to see exactly where the phone was. It even has the address of where it is. I called the police and they said "they can't do anything" even though i know exactly where it is.

What the hell is the point of the app find my iphone if the police won't do anything?

Added (1). The school won't get me the addresses of the people that live where i see the iPhone. And i'm not risking getting hurt over a phone

The point is more to go and get it yourself. Check the app next time you are in gym and see if the guy who stole it is there, then call the phone and see who it is.