Yes, unfortunately a scratch in this area is common. Touch-up blue might work okay if it could be confined to the scratch. The trouble is that bluing solution tends to flow into the surrounding area where it discolors the good finish, basically making the problem worse. So IMHO sometimes the best thing to do is to leave the scratch alone and consider it fair wear and tear.
BTW, I know a gentleman who applies blue to the scratches and dings on his guns with a pointed toothpick to confine the chemical to the immediate area of the damage. To my eye, his method works sometimes, but sometimes it doesn't.
YMMV.