Antonyms for the phrase "stayed hidden" could include "appeared," "surfaced," "emerged," "revealed," "exposed," "manifested," or "come into view." These words all suggest coming out of hiding or being visible in some way. Additionally, antonyms could include words that express movement or action, such as "moved," "traveled," "ventured," or "explored." These antonyms imply that the subject is not stagnant, but actively engaging with its surroundings. Overall, using antonyms for "stayed hidden" can add depth and variety to one's writing and help to paint a full picture in the reader's mind.