Brant Gardner notes that here in Alma 37:38 we have, for the first time, the name for the director or ball given to Lehi as recorded in 1 Nephi 16:10. This name is not in Nephi's record, so the name must have been given on the Large Plates. But why does Alma bring up the Liahona at this time, after so long in which we hear nothing of it? While we cannot know for certain, it is probable that it is because Nephi used the "small means" analogy with the Liahona in the Small Plates. It is a theme that Alma has picked up earlier in his charge to Helaman, and which he will highlight again in verse 41: "Nevertheless, because those miracles were worked by small means it did show unto them marvelous works. . . ." Those marvelous works came from "small means." In Nephi's description of the "small things" we find the following:
I Nephi, beheld the pointers which were in the ball, that they did work according to the faith and diligence and heed which we did give unto them. And there was also written upon them a new writing, which was plain to be read, which did give us understanding concerning the ways of the Lord; and it was written and changed from time to time, according to the faith and diligence which we gave unto it. And thus we see that by small means the Lord can bring about great things.
Alma describes the "small things" as follows:
it did work for them according to their faith in God; therefore, if they had faith to believe that God could cause that those spindles should point the way they should go; behold, it was done; therefore they had this miracle, and also many other miracles wrought by the power of God, day by day. (Alma 37:40).
[Brant Gardner, Book of Mormon Commentary, [http://www.highfiber.com/~nahualli/LDStopics/Alma/] Alma37.htm, pp. 14-15]