The only way I'd know to get that is from 2 places: one is your company IT team who handles emails. That's assuming it was sent, they should have a record of it somewhere/somehow. The second way would be a case to Support to have them pull a DB query to check if the DB shows the emails sent. They might have 1 or 2 other options to dig for it, but really someone in Support is going to be doing a lot of searching for the details.
If you go the Support route, start with a case under the Expense topic and Case Type of Emails/Email Reminders. I'd highly suggest asking for a call with Support as well to discuss the finer points of the request.
