I have in the past seen the owner+messages saved.? It's just difficult to get to.? What you do is go to your group online and login.? Then go to Admin/activity.? The default display is "all activity".? Filter it with the "message to +owner choice in the dropdown list and click on search.? You will find the one you want, the line looks like this:
I've changed the email address but the your signature line was the subject.? Note it says to owners via email.
John qpublic <john@...> sent message
"RE: Your Signature line" to owners via email
The weird part is I can't find any other way to get to it.
John