Actually, SkinnyBride2B, you DID put on weight. Precisely 0.4 Kg according to the scales.
This is why so many people advocate infrequent weighing.
Your weight will go up and down daily due to water retention and food bulk in your bowels. Scales will also vary due to environmental factors.
You can count on your weight varying over the course of a few days by as much as a kilogram or two. If your scales are reasonably accurate, then:
Yes, you probably DID put on weight!
You still lost fat.
The lost fat is hidden by the other sources of weight variance.
The weight of the fat you lose over a week can be easily hidden up by other sources of temporary weight gain, such as water retention and scale inaccuracies.
So don't worry, it's nothing strange. Just think of there being two types of weight: "fat weight" and "other weight".
Striving to improve in every way possible.