You really are a pompous piece of work. Rahner first used the term “implicit faith” and the “anonymous Christian” in the 1950s. So this term has had a specific meaning for the last 50 years.
Summa Theologica, II-II, q. 2, a. 6
"Whether all are equally bound to have explicit faith?""The unfolding of the articles of faith has been made with the passage of time... For the state before Christ, the faith of the ancients was founded upon the belief that God would deliver the human race, as appears from Job 19:25: 'I know that my Redeemer liveth.' [...] The minor ones, however, were not bound to explicit belief in these mysteries, as the 'majors' were; they were bound only to believe implicitly, in the faith of their elders."
Summa Theologica, II-II, q. 2, a. 7
"Whether it is necessary for the salvation of all, that they should believe explicitly in the mystery of Christ?""After grace had been revealed, both learned and simple folk are bound to explicit faith in the mysteries of Christ, chiefly as regards those which are observed throughout the Church, and publicly proclaimed, such as the articles which refer to the Incarnation... As to other minute points in reference to the articles of the Incarnation, men have been bound to believe them more or less explicitly according to each one's state and office."
"If, however, some were saved without receiving any revelation, they were not saved without faith in a Mediator, for, though they did not believe in Him explicitly, they did, nevertheless, have implicit faith through believing in Divine providence, since they believed that God would deliver mankind in whatever way was pleasing to Him."
De Veritate, q. 14, a. 11, ad 1
"If someone were raised in the forest or among wolves, and did what was in his power [facit quod in se est], God would provide for him what is necessary for salvation, either by inward inspiration, or by sending him a preacher of the faith, as He sent Peter to Cornelius (Acts 10)."
Facienti quod in se est, Deus non denegat gratiam