OMG wait til you get to chapter 22 and see what she suggests Lucretius might have intended to do to close the poem! She states that she doesn't claim the point is original to her but I agree I have not read it either and it is ingenious!!!
If she is correct then it is indeed easy to imagine that Cicero (or someone else) might indeed have "emended" the text to delete it!!!
This section is worth the price of the book and may be near genius (at least in my initial enthusiasm for it)!