Sending, receiving, and organizing email in Outlook.com
Hi, I'm John! I will help you with this.
A scheduled email should only be in the "Drafts" folder until the scheduled send time.
Have you already checked directly from Outlook Web here: https://outlook.live.com/mail? Please open Drafts there, then search by the recipient name or subject.
Also, did the scheduled send time already pass? If yes, please check Sent Items too.