If for some reasons an alert is removed or renamed, the monitoring job or dashboard alert cannot find the missing alert. The following approaches will be taken to resolve the situation.
For monitoring – An error email is sent. An explanation is included, e.g. alert <ALERT_NAME> not found in the template <TEMPLATE_NAME>.
For dashboard alert – An error icon is displayed in the template header. If you mouse over the error icon, you will see error message explaining the problem. If you are using the Dashboard Builder at that time, you can fix the problem immediately.
If a monitor check is missed, because server was not running, it will be run immediately after server is started. This is analogy to missed scheduled jobs. You can turn this feature on/off using Re-run Missed Schedule Jobs option in the Admin Console. Visit Section 1.4.1.3 - Server Options for more information.