Alright here's what seems to be the latest information regarding the recovery of documents and maps stolen from Madrid's Biblioteca Nacional (by way of partial update to yesterday's post).
AFP reports that a lawyer hired by the suspect (César Gómez Rivero) delivered eight documents, including two Cosmographia maps, to Argentinian police in Buenos Aires, "Argentina's assistant police commissioner Marcelo Elaide told Spanish radio Cadena Ser." The suspect "asked to not be arrested in exchange for having returned the items." Elaide added that "Argentine police have located the suspect but have not arrested him since they have not received a request from Spain."
Presumably that request will be forthcoming.