D&C 10

The Lord knows all things and has the power to do all things, but He has said -

"For my thoughts are not your thoughts, neither are your ways my ways, saith the LORD.
9 For as the heavens are higher than the earth, so are my ways higher than your ways, and my thoughts than your thoughts." (Old Testament Isaiah 55:8 - 9)

He has clearly stated -

"...the Lord God doth work by means to bring about his great and eternal purposes; and by very small means the Lord doth confound the wise and bringeth about the salvation of many souls." (Book of Mormon Alma 37:7)

The Lord knew Martin Harris would lose the 116 pages of the Book of Lehi. The Lord also knew that evil men would attempt to use the pages to trap the Prophet for -

"...behold, Satan hath put it into their hearts to alter the words which you have caused to be written, or which you have translated, which have gone out of your hands.
11 And behold, I say unto you, that because they have altered the words, they read contrary from that which you translated and caused to be written;
12 And, on this wise, the devil has sought to lay a cunning plan, that he may destroy this work;
13 For he hath put into their hearts to do this, that by lying they may say they have caught you in the words which you have pretended to translate." (Doctrine and Covenants Section 10:10 - 13)

The Lord has sufficient power to miraculously prevent this from happening. But He didn't. H He dealt with this in His own simple way. He said -

"Now ye may suppose that this is foolishness in me; but behold I say unto you, that by small and simple things are great things brought to pass; and small means in many instances doth confound the wise." (Book of Mormon Alma 37:6)

Years before, He inspired the Nephi to write a seperate record. A record that was very plain and precious. He also inspired Mormon to include this record with his abridgement. The Lord revealed to the Prophet Joseph Smith -

"...remember it was said in those writings that a more particular account was given of these things upon the plates of Nephi.
40 And now, because the account which is engraven upon the plates of Nephi is more particular concerning the things which, in my wisdom, I would bring to the knowledge of the people in this account—
41 Therefore, you shall translate the engravings which are on the plates of Nephi, down even till you come to the reign of king Benjamin, or until you come to that which you have translated, which you have retained;
42 And behold, you shall publish it as the record of Nephi; and thus I will confound those who have altered my words.
43 I will not suffer that they shall destroy my work; yea, I will show unto them that my wisdom is greater than the cunning of the devil.
44 Behold, they have only got a part, or an abridgment of the account of Nephi.
45 Behold, there are many things engraven upon the plates of Nephi which do throw greater views upon my gospel; therefore, it is wisdom in me that you should translate this first part of the engravings of Nephi, and send forth in this work." (Doctrine and Covenants Section 10:39 - 45)

"...thus we see that by small means the Lord can bring about great things." (Book of Mormon 1 Nephi 16:29)

By small means is His way.