Consider the possibility that a person was given the opportunity to hear (numerous invitations to hear God's Word) and accept the truth of the need to be water baptized but rejected all attempts when they could have in fact been obedient.
The instructions given on the Day of Pentecost were directed to everyone. "Repent, and be baptized EVERY ONE of you in the name of Jesus Christ for the remission of sins, and ye shall receive the gift of the Holy Ghost.
For the promise is unto you, and to your children, and to all that are afar off, even as many as the Lord our God shall call." Acts 2:38-39
Jesus specifically states that those not accepting His words are in fact rejecting Him. Everyone will be judged by the Word. Not just portions of the Word but all of it:
"He that rejecteth me, and receiveth not my words, hath one that judgeth him: the word that I have spoken, the same shall judge him in the last day." John 12:48
Beings everyone will be judged by the Word it stands to reason that all of the scriptures are accurate; this includes Jesus words on the topic of water baptism.
In each case just prior to Jesus' ascension He brings up the need for mankind's belief and the need for all to submit to water baptism:
“Go ye therefore, and teach all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Ghost: Teaching them to observe all things whatsoever I have commanded you: and, lo, I am with you alway, even unto the end of the world. Amen.” Matthew 28:19-20
“And he said unto them, Go ye into all the world, and preach the gospel to every creature. He that believeth and is baptized (water baptism) shall be saved; but he that believeth not shall be damned. And these signs shall follow them that believe; In my name shall they cast out devils; they shall speak with new tongues” (Holy Spirit); Mark 16:15-17
“Then opened He (Jesus) their understanding, that they might understand the scriptures, And said unto them, Thus it is written, and thus it behoved Christ to suffer, and to rise from the dead the third day: And that repentance and remission of sins should be preached in his name among all nations, beginning at Jerusalem. And ye are witnesses of these things.” Luke 24:45-48
Peter was speaking to a particular audience, therefore the command that all needed to be baptized needs to be considered in this light. If there was someone with severe health issues, or a prisoner who is unable to be baptized due to jail restrictions receives Christ, he is a believer regardless of baptism.
Speaking in tongues cannot be a sign of salvation because not all speak (spoke) in tongues. It was a sign in a specific context, in that it identified disenfranchised individuals throughout the book of Acts as true believers, and oriented them to the Jerusalem church by identical signs experienced in Acts 2 by them. This is covered well in a book called
New Wine by Dwight Pentecost for those who are teachable and want to look into this in more depth. Misunderstandings concerning Acts are common problems amongst aberrant groups.
It's pretty funny how you focus on the "name" in Matt 28:18-20.
If the pastor says, "I baptize you in the name of the Father, the Son, and the Holy Spirit for the remission of sins", would this person be saved? If not, what problem do you have with these words?
I have already covered Mark 16:15-17 and told you that Mark 16:9-20 is not canonical, but read those verses again. There is nothing said about a person who believes, but is not baptized. This case is not covered in those verses.
These are the possibilities:
1. Someone believes, and is baptized. - saved
2. Someone believes, and is not baptized.
3. Someone does not believe, and is baptized. - damned
4. Someone does not believe, and is not baptized - damned
The verses cover #1, 3,4 but doesn't cover #2. So, your proof text doesn't work.
By the way, you have inserted water baptism in the text. While I agree it is talking about water baptism, you really shouldn't interpret the text yourself. It simply says "baptized". You can be baptized in a spiritual sense, too.
As I have said, I believe baptism is a command, but it follows salvation, and is not necessarily accompanied by "tongues". This occurred in Acts, but you can find no other support for this teaching other than a historical account. There is no place in Scripture that teaches tongues is always the evidence of salvation. This comes from some within the Pentecostal movement, and largely Oneness Pentecostals.