For after that in the wisdom of God the world by wisdom knew not God, it pleased God by the foolishness of preaching to save them that believe. — I Cor. 1:21

God sent Cornelius a gospel preacher
Then Peter went down to the men which were sent unto him from Cornelius; and said, Behold, I am he whom ye seek: what is the cause wherefore ye are come? And they said, Cornelius the centurion, a just man, and one that feareth God, and of good report among all the nation of the Jews, was warned from God by an holy angel to send for thee into his house, and to hear words of thee. — Acts 10:21-22

God sent the Ethiopian eunuch a gospel preacher
And the angel of the Lord spake unto Philip, saying, Arise, and go toward the south unto the way that goeth down from Jerusalem unto Gaza, which is desert. And he arose and went: and, behold, a man of Ethiopia, an eunuch of great authority under Candace queen of the Ethiopians, who had the charge of all her treasure, and had come to Jerusalem for to worship, Was returning, and sitting in his chariot read Esaias the prophet. Then the Spirit said unto Philip, Go near, and join thyself to this chariot. — Acts 8:26-29 (Note: The Ethiopian eunuch was seeking God in His word, and God used the instrumentality of preaching to open his eyes. We don't find God merely through our personal efforts of study in the scriptures, He has ordained that through the foolishness of preaching that we would believe.)

God sent Lydia a gospel preacher
And on the sabbath we went out of the city by a river side, where prayer was wont to be made; and we sat down, and spake unto the women which resorted thither. And a certain woman named Lydia, a seller of purple, of the city of Thyatira, which worshipped God, heard us: whose heart the Lord opened, that she attended unto the things which were spoken of Paul. — Acts 16:13-14

God sent Saul of Tarsus a gospel preacher
And there was a certain disciple at Damascus, named Ananias; and to him said the Lord in a vision, Ananias. And he said, Behold, I am here, Lord. And the Lord said unto him, Arise, and go into the street which is called Straight, and enquire in the house of Judas for one called Saul, of Tarsus: for, behold, he prayeth, And hath seen in a vision a man named Ananias coming in, and putting his hand on him, that he might receive his sight. — Acts 9:10-12

God sent the thief on the cross THE gospel preacher
And he said unto Jesus, Lord, remember me when thou comest into thy kingdom. And Jesus said unto him, Verily I say unto thee, To day shalt thou be with me in paradise. — Luke 23:42-43

We hear the oft given testimonies of someone being converted under a false gospel (Arminianism)and later coming to a "better" understanding of grace, where in the scriptures does God use a man of lying lips who was not sent by Him for the conversion of His elect? One of two things can be said of this kind of conversion. One, they may not understand the way the Lord has graciously dealt with their soul, or, Two, they have been converted to a doctrinal position (Doctrines of Grace), but have never been born from above.