If you had a different KIND of food during those days off, that can cause a change in weight even if you didn't have that many additional calories.
You know how the first week on a new diet, most people lose a pretty big amount and everyone says "well, it's mostly water weight"? Well, if you were eating pretty cleanly, not too high carb, and with a focus on whole foods, if you ate a bit more carby and/or processed foods, your body rebuilds up the glycogen and with it, some extra water.
This is a pretty good explanation
http://www.phlaunt.com/lowcarb/19058097.php