Help identifying a part in iPhone 5
I work in a small repair shop in my town.
The other day a customer came in with a white iPhone 5 where the microphone didn't work at all.
Apparently he'd had a rather tech-savvy friend open it and replace something.
There is supposed to be a small ring that's missing inside the red area in the image linked bellow but that's missing.
The ring is connected to the part highlighted in yellow and that's the part i'm looking for, i've searched all the tear downs and repair manuals but I haven't found anything, help me? D: