What is this mystery metal piece in iPhone XR?

I am attempting to replace my iPhone RX screen. Unfortunately the first replacement screen I received was damaged so I had to wait for a second.

I notice that in the waiting time for the new screen to arrive, that a tiny piece of metal that seems to float between the lens gubbins and the new screen has disappeared! See the two screen shots from the how to video I am using. Does anyone know what this piece does? And more importantly, will the phone/camera work without it? Can a replacement be purchased?

Any help will be gratefully received. Thanks in advance.