The phrase "on scent" typically refers to tracking or pursuing a smell or scent. Antonyms for this phrase may include "off track," "lost," "disoriented," or "confused." These words can be used to describe a person or animal who is no longer able to follow a scent or has lost the scent trail. Additionally, words such as "unaware," "distracted," "ignorant," or "oblivious" can be used to describe someone who is not attempting to follow a scent or is simply unaware of their surroundings. Overall, the antonyms for "on scent" suggest a lack of focus, awareness, or direction.