Whatever happened, it is in the past and all you can do is move on. Although I find it hard to believe that you gained 10 whole pounds of fat in a couple of weeks, there are definitely other factors in motion there. Overeating/eating the wrong stuff would likely mean tons more salt which means yes... tons of water weight.
Anyway it doesn't matter now. It's just a number Lou, screw what the scales say. You have enough character to slap it back in the face and get some awesome results in the next few weeks to make-up for it and then some.
Maybe challenge yourself to work super hard over the next 28 days, do a 100% month or something and push yourself. That is a great way to respond after some disappointments.
Anyway, you know what to do. And I know you can do it, we all know you can do it. You just need to believe in yourself and work hard to make it happen! Think of yourself in another year, you will be miles away from your start weight.
KICK SOME ASS!