VICARIUS FILII DEI USED TWICE BY POPE PAUL VI IN OFFICIAL PAPAL DECREES

I will show you an evidence that the title "Vicarivs Filii Dei" was once used by the pope

VICARIUS FILII DEI USED TWICE BY POPE PAUL VI
IN OFFICIAL PAPAL DECREES

Vicarius Filii Dei was used twice by Pope Paul VI in documents found on the Vatican's web site. These are Apostolic Constitutions, which are the highest form of official Papal decree in the Roman Catholic Church and are issued with binding legal authority. Historically these decrees were known as papal bulls, the name referring to the lead metal seal (bulla) attached to authenticate the document. As a general rule, the superscription that opens papal bulls typically reads:

NAME (without ordinal number) EPISCOPUS, SERVUS SERVORUM DEI, AD PERPETUAM REI MEMORIAM

So, the following Apostolic Constitutions begin:

PAULUS, EPISCOPUS, SERVUS SERVORUM DEI, AD PERPETUAM REI MEMORIAM
PAUL, BISHOP, SERVANT OF THE SERVANTS OF GOD, FOR EVERLASTING REMEMBRANCE OF THE MATTER

Bafianae (January 11, 1968), Decree of Paul VI elevating the Prefecture Apostolic of Bafia, Cameroon, to a Diocese:

Acta Apostolicae Sedis, Commentarium Officiale, vol. LX (1968), n. 6, pp. 317-319. Libreria Editrice Vaticana. ISBN 8820960680, 9788820960681.
Scans: Title page - 317 - 318 - 319.

Adorandi Dei Filii Vicarius et Procurator, quibus numen aeternum summam Ecclesiae sanctae dedit, ...
As the worshipful Son of God's Vicar and Caretaker, to whom the eternal divine will has given the highest rank of the holy Church, ...

Vatican document confirms there is Vicarivs Filii Dei

The title appears in volume 99, page 21, in the entry for VICARIO DI GESU' CRISTO [Vicar of Jesus Christ], where it states very briefly that the

inscription VICARIUS FILII DEIis to be found in the VATICAN.

— Dizionario di erudizione storico-ecclesiastica da S. Pietro sino ai nostri giorni (Dictionary of Historical-Ecclesiastical Erudition from St. Peter to the Present), Gaetano Moroni

VICARIVS FILIIDEI is also Vicarius Christi