Whenever any person applies to the social worker to commence proceedings in the juvenile court, the application shall be in the form of an affidavit alleging that there was or is within the county, or residing therein, a child within the provisions of Section 300, and setting forth facts in support thereof. The social worker shall immediately investigate as he or she deems necessary to determine whether proceedings in the juvenile court should be commenced. If the social worker does not take action under Section 301 and does not file a petition in the juvenile court within three weeks after the application, he or she shall endorse upon the affidavit of the applicant his or her decision not to proceed further, including any recommendation made to the applicant, if one is
made, to consider commencing a probate guardianship for the child, and his or her reasons therefor and shall immediately notify the applicant of the action taken or the decision rendered by him or her under this section. The social worker shall retain the affidavit and his or her endorsement thereon for a period of 30 days after notifying the applicant.