Most of the grunts were fairly new. Those who had joined during Rocket's rebuilding, and probably weren't too familiar with the old ways of Rocket, or those who stood in their way. Even if Leaf stood out in the crowd, she wouldn't be noticed unless Giovanni himself caught sight of her.
He stood back for a while, some distance from the pokemart, observing the grunts inside. As he had expected, the cashiers seemed very reluctant to co-operate. He knew this was something he would have to intervene with personally.