Remote mic circuit wiring diagram

Hi, I'm trying to fix my mic volume control I can still get audio out but the remote is not working.I need help with the circuit wiring diagram for the Apple EarPods volume remote mic control. I have opened it and realised one of the circuit board negative solder contacts there's a wire missing,not sure if it's meant to be like that or the wire broke. I've checked all wires and didn't seem to find any loose wire hanging any help is much appreciated thanks.