The article is ambiguous on what object was actually 'kidnapped'. Other sources indicate it was an upper stage, presumably a flight-spec but unflown example.
It certainly wasn't a 'satellite' or an actual Luna probe.
It must have been an upper stage yes plus the spacecraft it carried, the dimensions mentioned by the article were way too small to be the whole stack with a booster.
It certainly wasn't a 'satellite' or an actual Luna probe.