The phrase "wert a party to" means being involved or participating in something. Some antonyms for this phrase could be "uninvolved," "disengaged," "unconcerned," "uninterested," "detached," or "unaffected." These words imply a lack of involvement or interest in a particular situation or event. However, it is important to note that sometimes being uninvolved or disengaged may not necessarily be a good thing, and may indicate a lack of responsibility or accountability. In such cases, it may be more appropriate to use words like "irresponsible," "neglectful," or "inactive" as antonyms for "wert a party to.