He can check with the court but most likely as the petitioner who did not appear his petition was dismissed. He would have to refile his petition and wait for another court date.
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This advice is not meant to create an attorney-client relationship and is a general anwer to the question posed.
If it was not hard to serve the mother, then he can simply re-file & re-serve his petition (assuming it was dismissed). If it was difficult to serve the mother, or he thinks it will be hard to serve her again, his other option is to file a motion to vacate his default, explaining the circumstances of his failure to appear along with stating a valid basis for his petition. In any event, if the friend is looking for a free, initial follow-up consultation with a Family Law attorney, please feel free to cal my Bronx office at 718-725-9600.