Along the same lines, I am thinking that we really ought to be focusing on the history of the transmission of Diogenes Laertius much more than we focus on Lucretius. As much as I love Lucretius and find that story of his influence to be fascinating and fun, the great bulk of epicurean ideas are in Diogenes Laertius, and Lucretius just provides additional detail which really doesn't change much. If you consider that Cicero preserved reference to the swerve to add to what is in the letter to herodotus, you really have virtually all of the important physics, epistemology, and ethics without needing Lucretius.
And although I would expect Latin was more widespread than Greek, it's my impression that the church scholars were almost as much fluent in Greek as in Latin, so the language barrier would have been little obstacle. And Laertius is such an amazing and fun book to read, i would expect (until corrected otherwise) that i would have been distributed about as widely as any other book on ancient philosophy.
I could be wrong about some of those points but transmission through Laertius really seems to me to be the key to getting a better perspective on what was "lost" and whether much of it ever really was in need of "rediscovery."