Don't waste your time beating yourself up for what's already done.
As for your weight gain, I've noticed that any time I stop Sole Sourcing and have anything to eat I see a big jump on the scales. I think part of the reason for these big jumps isn't necessarily the food choices that you made, but rather the difference between having almost nothing in your colon and perhaps even being a bit dehydrated, to eating a good meal and having food working its way through your digestive tract.
If you get back on Sole Source, the weight will drop away quickly as the food works its way through.
In my case, I've noticed that even one meal (even if well-planned, portion controlled, and made of good choices) can still put my weight up 2-5 lbs overnight.
Don't beat yourself up over it.