I clicked 'Send Later' and email vanished

If I don't want to send an email right now, I normally click 'Save Draft'. It works.

But this time, I clicked 'Send Later'. It closed the email I was composing, and appears to have deleted it. It is not in drafts. It is not in Sent Items. I was not given option of when I wanted to send it. How can I recover that email draft?