Chosen Solution

Where is this piece supposed to go? It fell out when I opened it

You may check out all these teardown and replacement tutorials, as I can see that the metal component can only be attached to the controller board, you may try your luck and find it there. https://www.youtube.com/watch?v=5P0Seo7e… Xbox One Wireless Controller Teardown Xbox One Wireless Controller Model 1708 Button Replacement

Is this the part that go on the side of the analog stick module where the joystick button is ?