Fritz doesn't find a coconut tree on the ground, but he does find a coconut. He trips over it early in his family's long adventure of shipwreck, when he and his father are exploring the tropical island. At first, Fritz jumps to the conclusion that it's a bird's nest, because the coconut has lost its protective green cover.
Fritz's father informs him that he is, in fact, holding a coconut. His father has been hoping they would find coconuts. He says to his son,
you need not necessarily conclude that every round hairy thing is a bird's nest; this, for instance, is not one, but a cocoanut.
Coconuts will become an important food source for the Robinson family, preferable to lobster. They will also be able to fashion the coconut shells into bowls.
As the parents recognize, the abundance of natural goods on the island, including coconuts, represents God's provision.