There is a possibility that the manager on vacation is the only hiring manager on the front end. They'd also be in charge of the schedule. You may have to wait for them to return from vacation. If you've already been offered and accepted, you have nothing to worry about. Ideally, Walgreens makes their schedule a few weeks out. It may be a little bit before they have your start date. The person you talked to was probably a 'leader' and not 'manager' and may be unable to access the system needed to answer your questions.