Nephi begins his plea to his brethren by invoking the desire to keep the commandments of the Lord. Surely Nephi's sworn oath to do so was impressive. What is interesting is the next step. Nephi is clearly one who has had the hand of the Lord upon him. He knows that this mission will succeed, and he is making every attempt to carry out that mission. Notice that it is Nephi's solution to the problem to present their riches to Laban for the plates. Nephi reasons that if Lehi left them behind because of the commandment of the Lord, that perhaps there was a reason in this action, and that the reason was to purchase the plates.
This idea, proposed by one who was clearly blessed of the Lord, reasoned out with acceptable logic, nevertheless fails. Regardless of the blessings of the Lord, we are always in situations where we must rely on our own best logic. That information may or may not be appropriate for the situation. It bears nothing on the designs of the Lord (other than as a constant reminder of the overarching importance of Agency). Those who have received much from the Lord remain as human as the rest of us, and not all of their, nor our, ideas or actions will be correct.