The result of this battle is the defeat of the Lamanites, and the removal of the Lamanites from the lands of Shilom and Lehi-Nephi. This does not require that the Lamanites be removed from Shemlon. In fact Shemlon will remain a strong base of Lamanite operations. There is simply a de facto truce between two close neighbors, likely including some trade and travel restrictions.
When the de facto truce is in place, Zeniff’s people return to their normal domestic tasks. Since the flocks and fields are the most vulnerable areas of the land, and particularly those on the south of Shilom, this appears to indicate that in addition to the military action some political agreement has been reached with Shemlon so that the people now feel safe in the fields, even though they would be more exposed there.