Bird,
Well, I'd say it's pretty hard to say exactly what the weight is that you gained. You'd have a better chance of knowing if you had taken some BF measurements before and after, but even that wouldn't tell the whole story. I'm really not sure how you measure water weight....I'm not doubting that you gained 10 lbs in a week, but I doubt very seriously that you gained 10 lbs of muscle. Hell, I bet the guys on gear over on the anabolics boards would tell you they never gained that much muscle in 7 days....If you did gain that much muscle, you'd be a physiological freak...I'd say you gained a few pounds of muscle, maybe some body fat depending on what you did with your diet that week, and some water weight....probably most of it being water weight. I don't know about others, but I measure my weight and BF about 5 days a week (on days I work out, because I try to record those stats along with my lifts in a journal I'm keeping), and I've seen my weight fluctuate as much as 4 or 5 pounds in one day, and my BF% fluctuate as much as 2 to 2.5%. So, I don't think you are lying about what you are claiming, but without knowing what your pre-1AD BF% and current BF% are, and without really having an accurate way to measure water weight, it's hard to say what the composition of your weight gain is.
Just my little $.02