Yes, sodium in your standard Americanized Chinese food is awful. That's more than likely where most of the weight is coming from. 1 pound of fat equals about 3500 calories and you know you didn't eat 14000 over maintenance in one day. Give it a little bit and you'll be back down.
That said, I loathe buffets. They always seem to encourage people to over eat, especially the frugal type. "I paid for it so I'm going to get my money's worth!" Where a frugal person goes to a regular restaurant and says "I'm only going to eat half so I can get two meals out of one meal (leftovers)".
Another thing I don't like about buffets is that many hands, faces and other things that close to my food. I know there are sneeze guards but they're not THAT effective. People reach over, sometimes use the same plate twice. Spend a little bit of time in a bathroom and you'll be surprised how many people don't wash their hands. The other thing is food safety. I worry about how long food has been sitting out. Call me paranoid but that cashew chicken isn't worth two days in the bathroom.
Sometimes we have no choice where we eat but I avoid buffets like the plague.