A fascinating story, indeed. However, if so many Christian manuscripts have been destroyed, how do we know? We do know that some 25000 whole and partial manuscripts of the New Testament exist today, from which our best critical editions are drawn. And think of all the pagan works that Christians preserved. For instance, the Arab Muslims are credited with bringing Aristotle to the West, and justly so — including important commentators like Avicenna. But they had his works because Eastern Christians preserved them.
Also, in Luke-Acts the disciples are not ready at the Ascension, but at Pentecost, and even then they were neophytes. Acts is about their learnings along the Way, so to speak.
It sounds as if this fabulous codex belonged to a minority church of which we otherwise have no trace.