Why ?
Changing Creator and Owner is not supported by Plone as Standard, (since one should never change a creator and ownership could be shared and take ownership is available under ZMI), but since it could happen because of migration problems I have added an function for that.
How ?
as Manager go to the object (document) and add to the URL "fix_user_creator?user=newoner" where newoner is the name (id) of the new owner like, ritsch, hans, fbar, ...
for example:
http://puredata.info/dev/pd_webwiki/whoownsme/fix_user_creator?user=PDuser
and back
http://puredata.info/dev/pd_webwiki/whoownsme/fix_user_creator?user=ritsch