There is a distinction between hiding and seeking a quiet place, and that is, it seems, what Simon does with some regularity, As early as chapter three of Lord of the Flies, by William Golding, Simon takes the opportunity to sneak away to a private place.
After he had spent all day helping Ralph with the shelters, Simon sneaks off to be alone as soon as he gets the chance. After picking some fruit for the littluns,
Simon turned away from them and went where the just perceptible path led him... He came at last to a place where more sunshine fell.... The whole space was walled with dark aromatic bushes, and was a bowl of heat and light.
Simon paused. He looked over his shoulder as Jack had done at the close ways behind him and glanced swiftly round to conﬁrm that he was utterly alone. For a moment his movements were almost furtive. Then he bent down and wormed his way into the center of the mat. The creepers and the bushes were so close that he left his sweat on them and they pulled together behind him. When he was secure in the middle he was in a little cabin screened off from the open space by a few leaves. He squatted down, parted the leaves and looked out into the clearing. Nothing moved but a pair of gaudy butterﬂies that danced round each other in the hot air. Holding his breath he cocked a critical ear at the sounds of the island.
Golding establishes early that Simon is a sensitive boy, so we should not be too surprised that he needs a sanctuary where he can somehow rejuvenate himself. The place he chooses is notable because it is the candle-bud bush Simon was in awe of in chapter one. He does not come here to hide but, as the above passage suggests, to think and meditate privately in the relative silence of the island.
Simon is considered by most to be a symbolic figure, representing Christ specifically and the soul or spirit more generally. It is not surprising, then, that he must find time to pray/meditate/think in a private, quiet place. Simon goes to his sanctuary when he can, and in one way it is an accident of fate that Simon is in his refuge when Jack and the others create their artificial sacrifice to the non-existent beast right outside this favored spot.
Symbolically, however, Simon is in this place just before he dies, perhaps symbolic of the Garden of Gethsemane where Jesus spends time before his death. Here he meets the devil in the form of the Lord of the Flies, and when he tries to reveal the truth about the human condition to the others (when he tries to tell them they are the beast and wants to save them from themselves), he is killed.