To audit activities on the Controller, you can run a one-time scheduled report requesting audit data, and that will show if someone has deleted the application or not.
To do so,
Log in to the Controller.
Navigate to Dashboards&Reports.
Click Create Reports.
In the Create Scheduled Report window, choose Controller Audit as the Report Type.
Complete the rest of the steps as given in the Reports documentation.
Hope it helps. Let us know how it goes. Don't hesitate to update the thread if you are still unable to track the audit trail.
... View more