The conch was found by Piggy but was retrieved by Ralph. The significance of this is related to the symbolism of the characters. Piggy is the most intelligent, the one who has ideas, but he is unable to get others to follow him. He has to pass ideas (and the conch) on to those with leadership capabilities (Ralph).
Piggy and Ralph find the conch in the novel when they are exploring the lagoon. They work together with Ralph working the palm sapling and Piggy reaching until they retreive the conch from the water. They then discuss how its valuable and how if you blew into its abdomen, it would emit a loud horn sound.the conch becomes a very important symbol of order and communication in the novel. It symbolizes communication and working together just as Piggy and Ralph needed to do in getting it out of the water.
In chapter one of The Lord of the Flies, Ralph and Piggy are exploring the lagoon together. The two boys are working well together, which is the first sign that this is going to be a key point later in the novel. The two boys are talking about their lives and getting to know one another when Piggy spots something in the water.
Ralph had stopped smiling and was pointing into the lagoon. Something creamy lay among the ferny weeds.
"No. A shell."
Ralph and Piggy work together again to get the shell free of the weeds. Ralph gets the shell out of the water and Piggy takes it and tells Ralph about blowing into the shell and making a sound. This conch shell becomes an important piece of power in the book. Whoever has the shell is supposed to be able to talk uninterrupted. Anyone who has read the book knows how well that works.
Piggy found it and gave it to Ralph to use to call everyone together