:::They don't "simply appear in a monastery."  You don't know what you're talking about.  Even beyond the fact that you are vastly simplifying the sources of ancient documents (Hint: Most don't come from western Europe at all, but from Byzantium)As I noted before, many classical papyri have been found in archaeological expeditions in Egypt.  There is also ample numismatic and monumental evidence to confirm the essential accuracy of the accepted timeline.