If the email was deleted, it might be in some "bin" / deleted folder.
If you are using the app and you get a notification, these are still available for a long time after they expire.
You can go online at MMB - when the page loads, just wait some time and UG offers eventually load. Alternatively, UG offers are prominently shown in the mobile app.

If you've missed it, you're probably missing on some ridiculously priced offer and the universe did might have done you a favour by taking the stupid option away from you.