It is part of the surround of the actual barrel.
There is normally a very small circular part in the plastic section of the key that talks to this transponder, if it has fallen out of the key you will have a small cylindrical hole in it. This is a known fault.
https://www.youtube.com/watch?v=n1BxI4xdaSsGood Luck.
p.s. Can you hear the fuel pump running on switch on - and do the dash warning lights come on or is it totally dead.
Could be the fuel pump relay if you can't hear it priming.