Is there a way to identify who deleted contacts are in email statistical reports?

We have noticed in our email stat reports (particularly the Email Analysis by Email Group report) over time we have "deleted contacts" in the reports. I ran an email report for a particular email group, then I clicked on the link for total opens which gives me another report called email analysis by email group - Total Opens. Alot of them we have determined are because people change their email address and then Eloqua no longer has any history on the old email address. Is there a way we can report on another unique identifier such as eloqua id to track a person's email history even if they change their email address?