In September 1827 Joseph obtained the abridged plates from Moroni's stone box in the Hill Cumorah near Palmyra. In the fall, Joseph and Emma moved to Harmony where Joseph began the translation. (JS-H 1:62)
After studying and translating the characters, Joseph translated the Book of Lehi from the plates. This were the 116 pages that were lost. Then, beginning in October 1828, Joseph resumed translating the book of Mosiah with Emma as scribe until Oliver arrived in April 1829.
When Joseph and Oliver neared the end of the abridged plates, they planned to re-translate the Book of Lehi. Instead, the Lord told Joseph he would have to translate the plates of Nephi to replace the lost 116 pages (D&C 10).
Except Joseph didn't have the plates of Nephi in Harmony.
The Lord instructed Joseph to write to David Whitmer so he could finish the translation at the Whitmer home in Fayette, New York.
Before leaving Harmony, Joseph gave the abridged plates to a divine messenger. Along the way to Fayette, Joseph, Oliver, and David met the messenger who was taking the plates to Cumorah.
The messenger brought the plates of Nephi (D&C 10) to Fayette, where he gave them to Joseph to translate at the Whitmer Farm. The messenger also showed the plates to Mary Whitmer.
David Whitmer as reported by Joseph F. Smith and Orson Pratt:
David Whitmer as reported by Edward Stevenson:
David Whitmer as reported by Joseph F. Smith and Orson Pratt: