The 16th and last satire breaks off mid-flow. The ending is lost, therefore, or perhaps was not written.
Ancient books were written on rolls. One modern author theorized that the end of a text ought to be safer than the start, because it should be inside the rolled up scroll. He seems to think that a roll would normally be stored ready to read.
But it seems to me, in my ignorance, that the reverse is the case. The average ancient reader would get to the end of his reading, and find his roll almost fully rolled-up. It is possible, of course, that some readers would then unwind the whole roll and roll it back up the correct way. But human nature being what it is, surely most of the time the reader will just pop the roll back in its cylindrical case. A reader who takes up a roll to read and finds it is back-to-front has an incentive to rewind it. A reader who wants his lunch has none.
I suggest, therefore, that as a rule most rolls were stored with the end hanging out. This would explain quite simply why so many ancient texts are mutilated at the end, without requirement for the hypothesis that they were written in codex form.