1. A communication system comprising: a mobile wireless communications device associated with an account including a numerically ordered master set of personal information manager (PIM) entries for a type of PIM data; the mobile wireless communications device configured to store a numerically ordered subset corresponding to the numerically ordered master set of PIM entries for the type of PIM data, the numerically ordered subset having fewer PIM entries than the numerically ordered master set; and a synchronization server ( 32 ) configured to synchronize the mobile wireless communications device and the account by mapping at least one PIM entry from the numerically ordered master set to fill the numerically ordered subset responsive to deletion of a PIM entry from the numerically ordered subset, the numerically ordered subset being reordered with the filled in at least one PIM entry from the numerically ordered master set to avoid blank PIM entries.