Scenario 1: Accidental Launch During Training Exercise
If the Navy "accidentally" launched the missile during an "exercise" it stands to reason that there would not be a NOTAM filed. However, were this the case, the Navy (or some other military entity) would likely have come forward with this information. But they have not... so we can likely rule out this scenario.
If we trust that there wasn't an exercise which involved the launch, and that it wasn't an accident, was it a defensive launch?