or to deleting it."
ughh..
there are myriad approaches to hunt down that damn column, for example by using powershell. here is an alternative, directly querying the content db
SELECT ct.ContentTypeId [ContentType ID] , Definition [ContentType Definition] , ct.DeleteTransactionId [ContentType DeleteTransaction] , ctu.ListId [List GUID using CT] , l.tp_Created [List Creation Date] , tp_DeleteTransactionId [List DeleteTransaction] , tp_FeatureId [Feature GUID] FROM ContentTypeUsage ctu INNER JOIN dbo.Webs w ON ctu.WebId = w.Id INNER JOIN dbo.AllLists l ON ctu.ListId = l.tp_ID INNER JOIN dbo.ContentTypes ct ON ct.ContentTypeId = ctu.ContentTypeId WHERE ct.Definition LIKE '%your column%'