This group of four is a small scouting party, carrying out a quick reconnoiter. The fact that they were willing to approach a royal excursion, which would have been armed, suggests that they had some way of recognizing that they had reached the people they sought. But if they did not know where they were going (v. 4), then how did they know that they had found the correct people? Mormon does not tell us.
The first possibility is that Nephites were so distinctive they could recognize each other on sight, suggesting the contrast between the Lamanite “skin of darkness” and Nephite fairness. Limhi’s guards mistook Ammon’s party for the outlaw former priests of King Noah, so Ammon and his party were not immediately classified as Lamanite. Nevertheless, the evidence of the text does not support an obvious difference in pigmentation that would allow for immediate distinction between Nephite and Lamanite. (See commentary accompanying 2 Nephi 5:21.)
The second, and more probable, way that Ammon recognized Limhi was that they had been directed to Limhi’s city by local peoples they had questioned. Ammon and his three companions were obviously outnumbered. They would not have approached a well-armed contingent in the open without some belief that they had found the people for whom they searched. Furthermore, because Ammon didn’t really know where he was going, it would be absolutely amazing if the very first people he happened to meet were the people he hoped to find. It seems more plausible that Ammon’s party asked about the people of Zeniff when they began to encounter small villages after they emerged from the wilderness. The smaller villages would not have standing armies, and it seems likely that rules of hospitality typical of rural populations would require them to assist needy travelers. In such a scenario, Ammon would have led a small party, not the whole group, into a village. The villagers would have not been alarmed by weapons for hunting; but if Ammon’s group were carrying military weapons (assuming a culturally known difference between the two types), the scouting party would have left them with the larger party. Since the people of Zeniff were tributaries to the Lamanites, the villagers wouldn’t see a small party searching for them as a threat to the Lamanite city that dominated the area. There would be no reason to prevent Ammon’s party from finding Zeniff’s people.
Culture: Though the discussion of Limhi’s rule is still in the future, it is worth noting that Limhi is considered not only a king but and a king over two lands: the land of Lehi-Nephi and the land of Shilom, south and slightly east of Nephi. Both of these lands were part of the original grant from the Lamanite king to Zeniff (Mosiah 9:6), retained through Noah to Limhi, in spite of the contentions and wars with the Lamanites. The implications of this grant will be examined later in the story of Zeniff. (See commentary accompanying Mosiah 9:7.)