Hermengild, St. Thomas DID teach Implicit Faith.
“Unbelief does not so wholly destroy natural reason in unbelievers, but that some knowledge of the truth remains in them, whereby they are able to do deeds that are generically good. With regard, however, to Cornelius, it is to be observed that he was not an unbeliever, else his works would not have been acceptable to God, whom none can please without faith. Now he had implicit faith, as the truth of the Gospel was not yet made manifest: hence Peter was sent to him to give him fuller instruction in the faith.” (II-II, Q. 10, A.4, Reply to the third)