After you delete an IMAP account in Microsoft Outlook 2013, and then you restore the IMAP account on that computer or you add the same account on a different computer, you notice that Contact and Calendar items are missing. This occurs even though you first synchronize the offline Outlook data file (.ost) with the IMAP account.
This problem is by design. Because of a change in Microsoft Outlook 2013 Service Pack 1, the .ost file is also deleted when an email account such as an IMAP or Exchange account is deleted from an Outlook profile. The .ost file that is associated with the IMAP account contains Contact and Calendar items. Therefore, these items are deleted together with the .ost file.
Microsoft is researching this problem and will post more information in this article when the information becomes available.