In Acts 8, the Ethiopian eunuch was baptized in water. Did Philip not understand the commandment of Jesus?
Just because I don't believe in baptismal regeneration doesn't mean I don't believe one is to be baptized in water after they are saved. Like the Lord's supper, it is commanded, and it is a proclamation of one's faith. While it is symbolic in nature, it is often accompanied by the sealing activity of the Spirit, of which the church is woefully wanting in my opinion.
As far as how one knows God, it is both through the word and the actual experience of His presence. The word tells us what is possible and the ways God makes Himself known. But actually having the things the Bible speaks of actually occurring in one's life...that is eternal life.
Why would Jesus would command His followers to apply that which is symbolic when His death and resurrection paved the way for the reality? It would be a complete waste of time looking for water to baptize people when they could be evangelizing. And yes, I do think Phillip didn't understand how everything was to work initially along with the rest of the disciples. Why should anyone be surprised by that? They were told to go and
make disciples of all the nations but then were taken aback when Cornelius, a Gentile, is incorporated. They had to learn the same way we all do and many a time it is through our mistakes that drives us back into the word of God to see where we went wrong.
Anyone who is not sealed with the Spirit doesn't belong to God. We are sealed when we believe, it is a part of what happens when we are baptized with the Spirit into Christ. Our experience does not teach us about God, it is that error that leads to cults. Our experience confirms God's word as true. A lot of the debates we have in this forum is because people rely on their experience to inform them of God's way rather than being informed by the word.
My life is what proclaims my faith, not getting wet. You see the command to be carried out by means of water, I see it carried out by means of teaching the truth. You can rely on water if you want, as for me I'll stick with the word and the Spirit to do what water can never do.