I think it is little bit arrogant from Russians to send relatively modern ballistic missile into enemy territory as remains of missile and MIRVs will be thoroughly studied by NATO and its allies. This can lead to better anti-missile technology.
There's nothing left to analyze after an object slams into the ground at 15,000 MPH. Beyond that, I guarantee the US already has the complete set of blueprints for it given our ability to expatriate sensitive information from other countries.