Question: Did the followers of Jesus ever just call him God? He is part of the Triune God, but did they ever address him as just God?
Answer: The “easy” answer is that as far as we know they did not. There is no recorded instance in which they addressed him in that way. My guess is, however, that you would like something a little more extensive than that simple answer. Following are some of the Bible passages that demonstrate that both the followers and the disciples realized who Jesus was.
Matthew, a disciple, records this concerning the worship of the baby Jesus by the Wise Men: “Where is he that is born King of the Jews? For we have seen his star in the east and are come to worship him.” (Matthew 2:2) “And when they were come into the house they saw the young child…and fell down and worshipped him.” (Matthew 2:11) Since Matthew was a Jew, he certainly knew the Old Testament references in Exodus, Deuteronomy etc. that the people were to worship God alone, and he would not have included this unless he believed that the baby Jesus was that God who alone was to be worshipped. This is especially important since the Wise Men were gentiles yet even they realized who this child was. Other New Testament people fell down at Jesus feet and worshipped him.
Along the same lines John, also a disciple begins his Gospel with these words: “In the beginning was the Word, and the Word was with God, and the Word was God. The same was in the beginning with God. All things were made by him and without him was not anything made that was made…and the Word was made flesh and dwelt among us, (and we beheld his glory, the glory as of the only begotten of the Father) full of grace and truth.” Clearly John believed that Christ was God who created the universe.
In John 6:69 Peter answers for the disciples: “And we believe and are sure that thou art the Christ, the Son of the Living God.” Same with Martha in John 11:27 “…I believe that you are the Christ, the Son of the living God which should come into the world.” Comment: If I have a son there’s no question he would be a man. And if God has a Son, there should be no question that he would be God. The disciples, Martha, and others understood this. (John 8:58 “…Before Abraham was , I AM.”)
In John 10:30 John quotes Jesus as saying: “I and the Father are one.” God himself confirms this in Matthew 3:17 & 17:5 “This is my beloved Son in whom I am well pleased, hear ye him.”
John 20:28 “And Thomas said unto him, My Lord and my God.”
The Apostle Paul (a follower) Rom.9:5, I Tim.3:16, Titus 2:13 etc. The writer of Hebrews ch. 1:8.
The above is only one way to approach the question of how the disciples and followers of Jesus viewed his deity. There are others.