Again, the human body is not a car. Gallons in equal miles out for a car, but calories in do not equal fat burned for a body. Or whatever you think the equation is.

Exercise - the extra walking - is holding water (addl weight) in your muscles, until they process it. THEN it might show a weight loss, IF you actually had to draw from fat stores, rather than just using any glycogen in your liver. Two days of walking does not burn fat. Unless you are walking 25 miles a day. Which i would not recommend. But you might want to look into training for the breast cancer walk, where they walk 25 miles a day for 3 days. But you work up to it slowly.

Where did you get this idea of instant fat loss? Its 3500 calories to lose one lb, and you have to pee it out, which means your body has to do all kinds of metabolic processes to convert fat to waste products.