Why has it taken so long for the "large metal object" to be identified. I mean, surely it didn't disappear did it? It's either on the side of the road, or still stick inside the car somewhere. Why can't somebody look and tell us all what object it was. I think that is a significant part of this story and shouldn't be left out.
I ran over one of these in my previous car:
it put 7 or 8 little punctures in the underside as it 'rolled' along under the car, before settling near the rear axle. That said, it wasn't particularly large, and just merged in with all the other detritus on the side of the road, it took me a long time to find it. It looks like this Model S drove/coasted for some time after the incident, so it might take a while to find the offending 'metal object' (although, since Tesla have described it as that, you'd think they would know what it was).