Gotta call BS on this “don’t know what it is” line. *Someone* knows...they’re just not telling. NORAD can identify a missle by it’s signature even if they weren’t aware of an impending launch, my guess is we are getting the official PR response that has been pre-planned in the event of certain events, including this one.
“We don’t know” is a safer response than “We know, but you’re not going to like the answer”.
I agree with Mindbender - they know exactly who launched this missile.
That said, what's your best guess?