Another case of this migrated-question-not-owned issue cropped up on Super User, so let's file a bug report to see if this is fixable.
- Question posted to SO 05:16z
- Question migrated to SU 05:22z
- User creates SU account at 18:00z
- User associates SU+SO accounts shortly thereafter
- missing: migrated question should have transferred ownership here
- User posts new copy of question at 18:31z
I'll try @random's workaround momentarily, but this process shouldn't require manual intervention.
Update: The workaround (disassociating the accounts and re-associating them) doesn't seem to work in this case. (Maybe it's me?)