If he bought it opened, the disk was returned by someone else opened. CC had checked the contents during that return. Besides, when selling customer an opened and relatively expensive item, an average salesman would open the box and show the contents to the customer. an average buyer would open and check the contents in the store.
If he bought it sealed, anyone would think WD would put a floppy drive in the box? WD doesn't even manufacture FDD.
Go figure.