Use this query to find where users have their post migrated but they never followed the question to the target site.
Q&A about the site for members of the workforce navigating the professional setting
SELECT OwnerDisplayName , Posts.Id AS [Post Link] , PostHistory.CreationDate AS [Migration Date] , Posts.CreationDate AS [Original Post Date] , CASE WHEN PostHistory.Comment LIKE '%stackoverflow%' THEN 'Yes' ELSE 'No' END AS [From Stackoverflow] , SUBSTRING(PostHistory.Comment,12,LEN(PostHistory.Comment)) FROM Posts JOIN PostHistory ON Posts.Id = PostHistory.PostId WHERE PostHistory.PostHistoryTypeId = 36 AND Posts.PostTypeId = 1 AND OwnerUserId IS NULL ORDER BY 1, Posts.CreationDate DESC