Save any wrappers during binge. Note unwrapped items. Enter data in nutrition tracker. You may be up several pounds, but calculate the calories of your indulgence. Divide by 3500, the calories of one pound. A binge of 875 calories means just 1/4 pound to lose plus the sodium/water weight. Do-able!
Don't give up. It's probably not as bad as you first thought. Give yourself 72 hours to lose the water weight, then the amount you need to lose to get back on track will be evident.