Relax.
First off, don’t confuse total body weight with fat.
What is more important is body composition - the amount of fat and the amount of lean body mass - which added together add up to your weight.
Now, no one can gain 10 lbs of anything in like a week unless you are on some INSANE cycle from HELL, you cant even get CLOSE to that. Well, to be more factual, you cannot increase TISSUE, wither fat or muscle, by that much in that time period.
So - what’s the 10 lbs?
Water.
Now in the case of dudes who load up on D-Bol, the water they carry is sort of "above normal". That’s why they get that "bloat" look. And you hear guys saying "man I gained like 10 lbs in a week! Cool!
Yeah, the scale shows that, but if and when they stop the DBol, chances are that almost all of that gets pissed away when their held water drops. (Yes, they will increase their lean mass some, but not THAT much).
This is also why in many cases guys whine about not keeping gains. Depending upon the regimen of gear and supplements, they will in many cases NEVER keep on all of the "weight" because some of it is NOT tissue - its water.
Now in your case, you were in the opposite direction.
Now I am not a biological chemistry god or anything, but my understand is that if you are carb-depleted, then your muscles are not able to hold onto as much water as they normally would.
So, if you are on a low-carb diet, you will weigh LESS to some extent just because your body cannot hold the amount of water that it did.
Yes, on low carb diets, you will start to lose and burn some fat. That’s true. Especially if its a very very low carb diet, and you get into Ketosis.
But even without the carbs being low enough to get into a ketogenic state, if you are carb-depleted, you will not be able to hold as much water.
So - what happened to you?
You have been low on carbs. You were not able to hold as much water as you normally would. And in that state you also burned some fat. Cool.
You carbed up. Your muscles can now hold more of a "normal" amount of water, and that’s what they did - about 10 lbs worth.
Its not fat. Its water.
And since we are talking about a situation of your being carb depleted, and then more "normal", this 10 lbs of water is actually like a ":normal" level for you, and for the most part you can keep it.