Cordoba is the second most populated province in Argentina. And with very clear skies. It's also a tourist destination. And since we are in summer vacations, the province is packed. Trust me, that if it had fallen there, it would have been on the news, big time.
It's also where the communications and tracking station for Argentine satellites is. So they would have even had a tracking radar right there. It must have fallen much before that.
I think we need to question your assumptions.
First, terminal descent is past the fireball stage [even the shuttle entry fireball has died out by the time it passes over Louisiana, for example] so the absence of sightings is not definitive. How many meteors are seen in daylight versus darkness -- a factor of 10,000 less? The more likely manifestation would have been sonic booms, which would hardly attract attention compared to thunder.
Second, I doubt any space tracking site is running full-sky constantly, or could really detect the size of the objects we're talking about.
The Cordoba region has been haunted by Russian rockets for decades, as Molniya-orbit vehicles perform their standard post-insertion apogee kick and then safety fuel dump, creating -- when they occur soon after sunset -- a glowing cloud crossing the skies. These apparitions have sparked UFO panics across the entire region. Nobody in Argentina ever figured them out.
I agree with JCM we're talking about the far end of the debris path, but not unusually so.