Here is how you can run a report to gather this information:
  1. Locate the email campaign the message was sent under and click "manage"
  2. Go to the deliveries tab
  3. Next to the delivery you want to examine, click "review"
  4. Under Related Actions on the left hand side, click "Delivery Recipient Report"
In this report you can see who was sent each version of the email. There will be a separate delivery review for both the A and B versions. You can export to Excel and do a search for the Constituent in question, or you can add the recipients to a group and check the groups of the Constituents in question.