The phrase "finding the key" has several antonyms, depending on the context in which it is used. For example, if you are talking about opening a lock, the antonyms could be "losing the key" or "not having the key." However, if you are referring to solving a puzzle or a problem, the antonyms could be "failing to find the solution," "giving up," or "quitting." In both cases, the opposite of "finding the key" implies a sense of difficulty, frustration, or uncertainty. Therefore, the antonyms for "finding the key" emphasize the importance of perseverance, determination, and creativity.