I was looking at the introduction to Catenae in evangelia aegyptiacae quae supersunt by Paul de Lagarde (1886; available at Lulu here). This is a publication of a Coptic catena on the four gospels, which contains a fair number of fragments of Eusebius, and that is why I was reading it. But then I noticed something more.
In the list of authors quoted, there is [didache twn apostolwn], given as p.73, line 7. A fragment of Chrysostom starts on line 10. So it’s only a short chunk. There’s no label against the passage (hence the brackets) which belongs to a chunk starting “Epiphanius” on line 1.
I don’t follow Didache scholarship, but I wonder whether this fragment has been noticed by scholars?
PS: I wonder how many people know of this bibliography of published Coptic texts, here: P. Cherix, Petite bibliographie des textes coptes litteraires edites? I encountered it just now, looking for stuff on De Lagarde. The site, http://www.coptica.ch/ seems to be very useful indeed. Here are links to texts; studies; manuscripts; and a mass of bibliographies. Wonderful!