William Clayton claims Joseph allowed Emma Smith to destroy the original manuscript to "pacify" her.
William Clayton, "Testimony," February 16, 1874, in An Intimate Chronicle: The Journals of William Clayton, ed. George D. Smith (Salt Lake City, UT: Signature Books, 1991), 558
“The revelation was read to several of the authorities during the day. Towards evening Bishop Newel K. Whitney asked Joseph if he had any objections to his taking a copy of the revelation; Joseph replied that he had not, and handed it to him. It was carefully copied the following day by Joseph C. Kingsbury. Two or three days after the revelation was written Joseph related to me and several others that Emma had so teased, and urgently entreated him for the privilege of destroying it, that he became so weary of her teasing, and to get rid of her annoyance, he told her she might destroy it and she had done so, but he had consented to her wish in this matter to pacify her, realizing that he knew the revelation perfectly, and could rewrite it at any time if necessary.