In reference to deletions, or missing portions of ancient scripture, please consider the following instance: In Matthew is the declaration that Jesus dwelt in Nazareth, "that it might be fulfilled which was spoken by the prophets, He shall be called a Nazarene" (Matthew 2:23). Is there any instance of this prophecy in the Old Testament? I haven't found one. I realize that there are prophets and prophesies that were never recorded, but it is possible that this was originally a generally known prophesy that was omitted as copies were handed down. If you think of the method in which records were copied, handwritten tediously, it is entirely possible that people, imperfect as they are, made errors in the copies. I know it sounds stupid and fantastic if you don't believe it, but the only way to really bring forth uncorrupted scripture is to hide them, and then publish them using God's gift as a means to translate them, without handing down copy after copy. It is miraculous, like finding the Dead Sea Scrolls.
The above is taken from a long letter defending various aspects of Mormon beliefs. I decided to break it up by subject.
One of the tenets of the Church of Jesus Christ of the Latter Day Saints is that the current Bible that exists has become corrupted over the years. While claiming to admire and study the Bible, Mormons leave plenty of room to ignore or deny things found in the Bible that are contradictory to their religion by claiming that it is one of those corrupted passages.
Yet the truth of the matter is that they are denying that God is capable of preserving His Word. Jesus stated, "Heaven and earth will pass away, but My words will by no means pass away" (Matthew 24:35).
You mention the Dead Sea Scrolls. One of the interesting things that came to light with the finding of the scrolls is the remarkable preservation of the Old Testament. Prior to this discovery, our oldest known copies dated to about 900 years after Christ. The Dead Sea Scrolls date to 200 year before Christ. Yet, in that 1,100 year gap there are only minor differences between our copy and theirs. God was able to preserve His Word.
But to use this as a comparison to the Book of Mormon is almost laughable. The Book of Mormon did not exist in the world prior to the 1800's when Joseph Smith produced it. There is no mention that anything even close to it existed in anyone's knowledge. There is nothing to compare it to. You want to say that God preserved His Word by hiding the Book of Mormon, but that claim means God hid His message from the world for thousands of years. The introduction of an unknown book offers no proof that God preserved His Word. It forms no evidence that the book originated from God. The Bible is not is not the same. It has existed.
You claim that Matthew 2:23 proves that prophecies were lost. However, to make that conclusion, you must assume that Matthew was quoting a specific prophecy. Yet, read the passage again and you will find that he doesn't say a prophet said this. He said prophets said this. In other words, Matthew is summarizing a point made by several prophets. I discussed this at length with someone who wanted to deny the inspiration of the Bible by using the same verse. You can read it in "Did Matthew fabricate a prophecy to support his claim that Jesus was the Messiah?"