It is extremely significant that the townspeople lost the original lottery paraphernalia. In addition to the reasons stated in the previous post, the loss of the box is significant in that it symbolizes the idea that the people in the village have no idea why they have to partake in the lottery. Like many traditions, it just is.
In the story, only one person—Old Man Warner—seems to really remember any reason why the lottery has to be held, who states a saying, "Lottery in June, corn be heavy soon." Then he goes on to discuss what he sees as dangers to abandoning the tradition like those in the north village.
In addition to the lost paraphernalia, other traditional actions that accompanied the lottery had been lost or changed. The villagers used paper instead of wood chips for the names, the "tuneless chant" that preceded the lottery had been abandoned, and the "ritual salute" had also been forgotten.
All of these suggest the idea that traditions are sometimes carried out despite people not knowing the reasons for carrying them out. While, as Old Man Warner points out, the lottery might have originally been held as a sort-of crop sacrifice, the lottery at the time of the story seems to be held as a way of sanctioned killing as evidenced by the boys' excitement of gathering rocks at the beginning of the story.