I get the "from outside our solar system" part, and it seems believable that sensors designed for missile tracking would get enough telemetry info to establish that.
But the "tougher than iron" part? Based just on how much material was lost during atmospheric entry, as reported by sensors not really designed for that purpose? That's a tough pill to swallow. It would be really interesting to hear more about how much this asteroid differed from others measured by the same equipment.
I have a dim memory that missile tracking systems pay close attention to how fast an object decelerates when it hits atmosphere, as part of distinguishing real warheads from decoys. Maybe you can use that data to estimate how fast a rock is eroding að it falls.
But the "tougher than iron" part? Based just on how much material was lost during atmospheric entry, as reported by sensors not really designed for that purpose? That's a tough pill to swallow. It would be really interesting to hear more about how much this asteroid differed from others measured by the same equipment.