In a Workflow Task ad-hoc query, no results are returned using the filter "Status is equal to Canceled". However, if the filter "Status is not one of Open, Completed" is used, you can find Workflow tasks that have been cancelled (the status is spelled that way in the database).
Both 'canceled' and 'cancelled' are correct spellings in the US and have been used interchangeably in portions of CRM. At this point to ensure backwards compatibility is not broken we must keep some of these spellings as they currently exist in CRM.
The solution is to edit your query using the filter of 'Status is not one of Open, Completed'.
Steps to Duplicate
1) Go to Analysis > Information Library > Add a Workflow Task ad-hoc query 2) Add the filter "Status is equal to Canceled" > Preview results 3) Notice that no results are returned. 4) Go back to the query filters > Delete the existing filter > Add the filter "Status is not one of Open, Completed" > Preview results 5) Notice that the returned results all have the status of Cancelled.