The Loeb blurb comments, "and Tryphiodorus (papyri reveal the correct spelling to be “Triphiodorus”) deals with The Taking of Troy in 691 lines, beginning with the Wooden Horse and ending with the sacrifice of Polyxena.".
These papyri cannot be the one from Oxyrhynchus, P.Oxy. XLI 2946. The evidence of the documentary papyri can be assembled through Trismegistos People.
If the first member is τριφι-ο-, the Graeco-Egyptian deity Triphis is involved in a name with a geographically restricted distribution.
Lexical studies (Italian).
M.L. West wrote in Gnomon 42.7 (1970), 657-661 at 661, of Livrea's edition of Colluthus: 'I hope that Livrea will persevere with his edition of Triphiodorus ; that he will give it a more comprehensive introduction, a less constipated apparatus, and a better-balanced commentary; and that he will stop spelling the poet's name with a y.'.
LGPN knows no bearers of this name at this date of either spelling.