I do not believe he was.So you're saying that Nicodemus wasn't a 'secret disciple for fear of the Jews' in Jn 3, but was in Jn 19. I say he was, it's why he came to Him by night. Like a moth attracted to the light. John 3:21
Salvation is not the topic (other than 'entering' in v 5), born of God/born from above/born of the Spirit is the topic.