The elephant might be a symbol of power. Its vanishing could represent the loss of power in a certain context.
The elephant may also stand for something that is out of place or doesn't belong. Its vanishing could be a way of the story's world trying to return to a more 'normal' state, as if it was an anomaly that couldn't be tolerated. However, this act of vanishing also leaves a void, which might be the point of the story, to show that even things that seem out of place have a role to play and their removal has consequences.
It could be a sign of the exotic or the unknown. The elephant is not an ordinary animal in most settings. When it vanishes, it may be about the loss of the allure of the unknown. For instance, in a community where the elephant was a source of wonder, its disappearance might make the place seem duller. The story could be using this to show how important the element of the unexpected is in our lives.