Day: 20th, three hours
Searching floors: 1, 2, 3, 4, 5, 7, 8, 10, 11, 12, 13, 14, 15, 18, 19, and others she won't be able to get any candy on because of the fifteen floors rule
Method: Scanning from the staircase, then checking through it more thoroughly, then moving on to the next floor once she feels that she's looked through it enough. She would go back to floors later but that won't work :<
Accompanied by: Nobody