The investigation established that the citation Trithemius gave cannot be traced in the works of Pietro d'Abano, and that the one Sworn Book manuscript carrying the alphabet took it from Agrippa, who had it from Trithemius. That closes the route by which the script was said to be medieval. It does not close the possibility that a witness survives somewhere unexamined, and it names nobody as the maker, so the origin of the letterforms is still an absence rather than a settled sixteenth century invention.
What would resolve this A pre-1518 manuscript carrying the letterforms, found in the Solomonic, ars notoria or alchemical manuscript traditions, or a systematic survey of those traditions returning nothing, which would be a real answer rather than a failure. Failing either, a study of Trithemius's own working papers establishing whether he devised the script himself.
OpenHistory of Renaissance occultism; codicology of late medieval Latin magical manuscripts; history of cryptographyHonorius of Thebes; Joseph H. Peterson (ed. and trans.), The Sworn Book of Honorius (Liber Iuratus Honorii), Joseph H. Peterson's edition