What is this extra part after replacing charging dock

Verizon iPhone 4s 16gb - My alerts & music randomly stop working, so I found on here that I needed to replace the charging dock, so I got a new OEM part on eBay.

When I disassembled, a part came off the phone & don't know where it goes.

It is a very small metal square, one side is black & the other side is gold. It also has a tiny black arm with a gold dot at the end... looks kind of important.

Everything on the phone works, EXCEPT I'm getting a USB Not Recognized error on Windows PC.

Please help!