After Mrs. Krabappel confiscates all the cell phones from the class, the next shot of the angry class shows they all still have their phones on their desks, but all the phones are twisted and broken.
When Edna confiscates the students' phones, she dumps the box in the drawer with the biology frogs. When Zachary hands the phones back, he pulls the whole box out of the desk. Not only would the box not be in the drawer, it was likely Edna's own box, likely used for her personal effects when she was fired.
When Edna is about to eat her goddess bar, The sleeves of her pyjamas are visible in a closeup but in the next frame she is dressed in her standard outfit.