While there are many antonyms for the phrase "am on the scene," some commonly used ones include "absent," "missing," "absentee," "non-existent," and "not present." These words indicate that the speaker or subject is not physically present at the scene in question or is not involved in the situation at hand. Other antonyms may include "unseen," "invisible," or "unnoticed," which suggest that the person or thing in question is not visible or easily noticed. Whatever the antonym used, it is clear that "am on the scene" implies being actively present and involved, while the antonyms indicate a lack of presence or involvement.