Very common to see this, in fact it's the norm if playing curtain roulette. I'm not sure when your flight is, but particularly if you are within 72 hours then you will be moved, maybe by one row, maybe by 15 rows. If playing curtain roulette (and there are dozens of threads on this elsewhere) you have to keep an eye on this at least daily and be prepared to accept you may not win the game. If you were given an OpUp, MMB would tell you.