It is the job of the manager or assistant manager, according to the handbook, not the shift. I have a picture of that paragraph and I just double checked.
>in the event of sudden sickness, injury or emergency, or when the partner is using paid sick leave allowable by law, the partner will not be held responsible for finding a substitute, but must still notify his or her **store manager or assistant store manager of the absence prior to the beginning of the shift so the manager can arrange for shift coverage.**
Edit:
$1 is a pic of the sentence.