This problem kept me occupied for a stretch this morning. Finally, I think I have all the steps down:
1. If you have deleted all occurrences of the use of the content type, then check your recycle bins
2.Delete from site recycle bin.
3.Delete from Site Collection > Site Settings > Site Collection Administration > Recycle Bin.
4.Delete from End User Recycle Bin Items.
5.Delete from “Deleted From End User Recycle Bin.”
6. Use the following PowerShell script to check for left overs:
$site = Get-SPSite “http://sharepointsite”
$rootweb = $site.rootweb
$sc = $rootweb.Fields[“name of one of the site columns to locate”]
write-host ” Found Site Column ‘” $sc.Title “‘ in gallery” -ForegroundColor Gray
foreach( $listusage in $sc.ListsFieldUsedIn() )
$listID = $listusage.ListID
foreach ($subweb in $site.allwebs)
foreach ($list in $subweb.lists)
if ($list.ID -eq $listID)
write-host ” Site Column ‘” $sc.Title “‘ used in list ‘” $list.Title “‘ in site ‘” $subweb.Url “‘” -BackgroundColor Yellow -ForegroundColor Black
7. Or try this one:
$web = Get-SPWeb -identity sharepointsitename
$column = $web.Fields[“display column name”]
This will give you the UID of the list that you can then determine