According to the rules, the cue ball that scratched is considered to have been driven to a rail:
8.4 Driven to a Rail
A ball is said to be driven to a rail if it is not touching that rail and then touches that rail. A ball touching a rail at the start of a shot (said to be “frozen” to the rail) is not considered driven to that rail unless it leaves the rail and returns. A ball that is pocketed or driven off the table is also considered to have been driven to a rail. A ball is assumed not to be frozen to any rail unless it is declared frozen by the referee, the shooter, or the opponent. See also Regulation 29, Calling Frozen Balls.
Consequently, all requirements of an opening break have been met.