Surely you can recognize another employee's voice? Anyway, if it's not the employee in question calling, never give out any personal information about another employee unless that employee has explicitly said to do so. Even if the person tells you they know the employee in question and he/she said it was okay for you to give out the information, you still don't give it out unless you are told by the employee that it's okay. That's not just Kroger policy. That goes for any place of employment.
I've always been told to never give out info like that over the phone (unless you know it's them calling for their schedule or whatever). Idk if it's an official policy though.