Theon of Smyrna, under Hadrian, is the name this site attaches to a Greek Platonist from Smyrna, not Theon of Alexandria.
What this site holds is Commentary on Pindar’s Twelfth Pythian Ode as fragments in Porphyry, Testimonies, and Homeric commentary fragments. Mathematics Useful for Understanding Plato is the book later readers attach to this name; it is not the work list here. On the Order of Plato's Writings and On Mathematical Signs are lost or spurious in the notices. It is these headings, not a hidden Timaeus handbook.
Available Works
Commentary-the Twelfth Pythian of Pindar
Ὑπόμνημα εἰς τὸν Πίνδαρον Πυθιονίκην ΙΒ'
2 passages
Testimonies
Μαρτυρίαι
8 passages
Theon's Homeric Commentary Fragments
Ἀποσπάσματα
13 passages
Also published as PDF.