It must be a typo.

Function calls have the highest priority here, followed by logic NOT and logic OR.

    !didIMakeAMistake() || CIsWrongHere();

!didIMakeAMistake() is evaluated first (or you can say didIMakeAMistake() is executed and evaluated first, then its result is inverted and checked), if it's true, evaluation is finished. If it's false, CIsWrongHere(); is evaluated.

It is indeed equivalent to

   if (didIMakeAMistake())  /* !didIMakeAMistake() == false? */
      CIsWrongHere();

Without the invertion.