Oh man, did you ever send me down a rabbit hole this morning! You are not wrong, such a report did (and does) exit. But because it's not strictly an aviation report, it's not in the CARS. Heck, it's not even in the CASRs. The information was located in the AIP.
It is known as a CIRVIS (Communication Instructions for Reporting Vital Intelligence Sightings) Report, and the list used to include things like invading armies or unidentified surface warships and submarines.
You can find the reporting information in
AIP Section 1.14.2.1. The
AIM (the domestic version of the AIP) only references CIRVIS reports once in section 1.1.2.1.
What you and I learned was probably closer to
this.