It would seem to my layman’s mind that if one of the drones or whatever is shot down over desolate territory (say the NJ Pine Barrens) it could readily be determined where the base metal of the object originates; there should be other indicators showing its source, as well. And if it is an exotic, heretofore unknown metal, then we may need further investigation.
You’re overthinking this. Simply look at the motors and electronics, duh?!