Even if you do have a gain this week, the main thing is you'll know why. You had a good night out, it wont happen every week so dont worry too much.
Make sure you drink lots of water, I find when I have pizza I retain loads of water after. Not sure if there is quiet a high amount of sodium or if it its the dough?
You pulled it back tonight, you could have easily blown it thinking you'll eat the buffet and the cake "because I've gained anyway so I may as well carry on"! - but you didn't!
You may surprise yourself Monday. Dont look at your own scales, just go with the SW ones. Mine are always different from SW so I use them as a rough measure mid week but never get hung up on it or pay too much attention to it.