According to Sidney Rigdon, when the excerpt from the Book of Enoch was revealed to membership of the Church in Jan, 1831 (Moses 7-9), there was “much conjecture and conversation” stimulated by the idea of “lost books”. Rigdon specifically mentions the Biblical Book of Jude:
“Much conjecture and conversation frequently occurred among the saints, concerning the books mentioned, and referred to in various places in the Old and New Testaments, which were now no where to be found. The common remark was, they were lost books; but it seems the apostolic churches had some of these writings, as Jude mentions or quotes the prophesy of Enoch, the seventh from Adam.”
The Times and Seasons Vol. IV. No. 22. City of Nauvoo, IL. October 1, 1843.