A similar case, I once missed a payment to my credit card company because I did not receive the bill. No surprise, as they send me a bill only if there is an outstanding balance. So I called them to explain the situation and they wanted some security questions. One of them was, how much was your last bill? D'oh!

Your case is understandable. The poor guy at Apple support would of course have no access to HR documents. You could try to escalate your case in writing and hope but do not expect it sorted out quickly. It may take weeks.