Joseph Smith taught that there was an apostasy after the death of the apostles and that the "Church" (priesthood authority) was taken from the earth. He taught that "evil and conspiring men" had deliberately edited the Bible and inserted errors.

“My object in going to inquire of the Lord was to know which of all the sects was right, that I might know which to join. No sooner, therefore, did I get possession of myself, so as to be able to speak, than I asked the Personages who stood above me in the light, which of all the sects was right (for at this time it had never entered into my heart that all were wrong)—and which I should join.

I was answered that I must join none of them, for they were all wrong; and the Personage who addressed me said that all their creeds were an abomination in his sight; that those professors were all corrupt; that: “they draw near to me with their lips, but their hearts are far from me, they teach for doctrines the commandments of men, having a form of godliness, but they deny the power thereof.”

He again forbade me to join with any of them;"  Joseph Smith History 1:18-20

No Apostasy

Is God a liar? Can man corrupt something God declares will not pass away?

“And I say also unto thee, That thou art Peter, and upon this rock I will build my church; and the gates of hell shall not prevail against it.” Matt 16:18

“Ye have not chosen me, but I have chosen you, and ordained you, that ye should go and bring forth fruit, and that your fruit should remain: that whatsoever ye shall ask of the Father in my name, he may give it you.” John 15:16

“And in the days of these kings shall the God of heaven set up a kingdom, which shall never be destroyed: and the kingdom shall not be left to other people, but it shall break in pieces and consume all these kingdoms, and it shall stand for ever.” Daniel 2:44  

This last scripture was made before the New Testament, not after Joseph Smith "restored" the Church. The real New Testament Church of Christ with the original Apostles, teachers, evangelists, and so forth. That is the one that will stand forever.