Shifts overlap, so whoever is there when they leave will take over. Sometimes we have had 2 employees try to cover the whole floor and I have had many many people ask me (a cashier) where to fine something on the floor. We all have to know where to find something so we can help, even if we are approached when on lunch or going home.
Many times I have been asked when walking thru the store to leave, and I show them where to find something and answer their questions.