Creating in incident from e-mail and event monitor from only the userid, not the customer display name

We are trying to create an incident from an email that only has the userid (samaccount) available to us.  We have not been able to create the incident, since we cannot determine the customer display name associated with the userid.  If we log the incident from the desktop client, we can enter the userid in the requester field and the name populates.  The customer internal table has the userid and customer display name in it.  How can I pull the customer display name for use in the email monitor to create the incident or use the userid to create the incident?  We are on version 8.3.2.