Hello portbhoy. As mentioned above you have a good insight on the part being a piece of spring. But what surprises me is that this would fall out of a car as recent as a Fiesta ST which means it no older than roughtly 2 years. So this begs the question... Are you driving an ST? Not that it makes any difference but I've re-read the thread and there is no mention of your car in it and I'm just worried about this rust level on such a recent car. Other than that a small introduction would be nice if you can spare 5 minutes...