Been there, done that.
Apparently, they wouldn't deprive you of your efforts, and I've completely missed it during the time I did it, so yea, ultimately, I think it depends on the marker him/her-self. I do know that I forgot to write the question number for the Chinese composition (Singapore) and I've gotten a B3, obviously, they've taken it into account. I GOT A DAMN B3 BECAUSE MY ORAL EXAM (Pass). SCREW IT. Finger crossed, pray the dude (Cambridge) is not that evil enough, or be as kind as the Singaporean counterparts.
Furthermore, if your registration no. is in-between your classmates, chances are, he's gonna ignore the (either) (or) selection because he's gonna judge you base on your answers anyway, and possibly tired of refering back and forth the papers. Unless you're undoubtably out of point, he checks the question requirements, you're screwed.
Most likely, you'll be fine, don't worry. There's no way for you to access the scripts anyway (unless you wanna pay that 100$), let your results tell the picture.
Relax.






