Howdy John!
I would love to help you with this. Based on what you’ve said I’m think the file you are looking for is located here: /wp-content/plugins/event-tickets/src/views/tickets/email.php
If you need further assistance would you mind logging in so I can verify your support access? Or, if you don’t have/want a license (which includes a year of support) you should checkout the volunteer community on WordPress.org: The Events Calendar. It’s not the same level of support, but it’s free! We even check those forums once each week and help to the extent we can.
Cheers!
– Brook