You can lose 2lbs by eating sensibly and exercising.
Starving yourself like that is setting you up for a binge
what you ate was only about 400kcals. You could burn that off in 1 aeorbics lesson and 400kcals = 0.1lbs of fat - even if you were to put on weight from your "binge".
If your scales are up today it's most likely that you're retaining water from the sodium in the food you ate.
Best bet is to drink plenty of water, get lots of fruits and veggies in your diet, eat a portion of lean protein at lunch and dinner with some whole-grain carbs like wholemeal bread, jacket potato, brown rice, brown pasta or oats.
When you crash diet you lose mainly water and MUSCLE MASS
Which is very scary, since muscle is the main thing in your body that BURNS calories.