Hi Krwelliver,
As I understand it, some tasks have been moved to the Deleted Items folder in Outlook 2013.
If this is the scenario, I would suggest you follow these steps:
1. Start Outlook 2013.
2. Press CTRL + 6 to show the folder list.
3. Select the tasks in the Deleted Items folder and drag them to the Tasks folder.
Moreover, since this can be Outlook client side issue, I would suggest you visit or dedicate Outlook 2013 forum for further support. Thanks for your understanding.
@Adadson and Jarleeuw,
Thanks for your help on the issue.
Best Regards,
Bruce Zhou