The Nephite Practice of Burying Treasure unto the Lord
In the following verses we learn that the people buried treasure so as to hide it from their enemies, as they themselves fled for their lives. The Lord answers this by saying that if they are going to bury treasures for any reason then it should be unto Him. Some would argue that this reference to buried treasure is a throwback to Joseph's own treasure digging activities and magical beliefs. His culture and beliefs certainly play a role in coloring the English translation of the book, as is the English translation's dependence on the King James Bible.
To understand the Book of Mormon, we must read it as the translation of an ancient book, as it demands us to; we must read it under the lens which it provides for us, the lens of antiquity. Studying the book only at the translation layer, which is what fictional interpretations are limited to, will only give us superficial readings. Nephite religions were very different from those of their distant Near Eastern cousins. I think Helaman 13:19 is referring to the mesoamerican practice of caching, which was happening at Chiapa de Corzo at the time the Book of Mormon refers to it. What are caches?
Lowe defines caches at Chiapa de Corzo as “one or more objects which appear to have been buried as a votive offering unassociated with a burial” (Lowe 1960:55).(Source).
The Lord speaks to people in their own language, in a way that they will understand. It seems that the Lord was castigating His people for their materialism by referring to a mesoamerican religious practice that they were familiar with.