Cosmos 482's orbital data and reentry predictions were publicly available from the US Space Force via USSPACECOM's space-track.org service.

It was tracked for decades as object number "NORAD 6073" and anyone with a sufficiently-capable observation apparatus could have imaged its reentry.

Provided they were in the middle of the Indian Ocean, of course.

It will be difficult to get an exact final position because the space surveillance network points up, not down, and it was behind the horizon from the GEODSS at Diego Garcia anyways, and ballistic missile radar coverage does not extend to the Indian Ocean.