The policy should have clearly defined what is to happen during call situations, which it obviously didn't, considering it "couldn't be found" by the manager. I would guess that the manager knew their actions could be considered inappropriate, but wanted to fluff her authoritative feathers hoping you'd take the bait without questioning her.
It is appropriate to call someone before their shift, if parameters are clearly defined and expectations are understood. At one facility I work for, we are notified an hour before our shift if we will be getting put on call, or at the other facility we assume pre-arranged call schedules. Most people are awake an hour before their shift, so this is acceptable. If possible, they will notify us up to two hours in advance, but are only required to do one hour. It prevents staff that commute long distance from hitting the road and then having to turn around (it is a rural area so many people commute long distance, and winters here are long and treacherous with frequent road closures and unplowed roads).
There may be more than one person on call, so a person is able to inquire whether they are 1st in, 2nd etc. This is especially important during holidays with low census and our annual Christmas gift of increased patient to nurse ratios. We want to know if we are safe to stay in pajamas until lunch time or if we need to be dressed and ready to go by 0700. There is a certain algorithm used to determine call rotation, and most people keep a general idea of when they could reasonably expect to be placed on call. Call runs for the scheduled shift only and starts respectively with call pay. We can be notified of being on call an hour beforehand, but since call and pay start at say 0700, we cannot be called in until 0700 or later. This basically eliminates the need to notify the call person to be there right at 0700, because staffing would know they were needed and would never make the phone call to put the employee on call. Once called, we have either 20 minutes to a half hour to get there depending on the facility. So, if we're called in at 0701, we have until 0731 to punch in at the one facility.
It's expected that our charge nurse and the potential call staff will communicate at the time of on call status about the likelihood of getting called in. The call person should be made aware of whether they are first or second in, if there are pending surgical patients etc. and when they are expected to arrive to the unit if so. This gives staff an expectation and level of comfort while on call. There are some other minor details about our call, but the point is that everyone needs to be on the same page and there should be a clearly defined policy describing expectations.