1. Remember some keywords like Sender’s name, subject or title body of the email in your lost message which will definitely help you finding the mail.
2. The search box will be visible on the top of your Gmail account with the title of “Search”, find or any other title which point suggests searching.
Enter your keyword into the search field and select on search.
3. Enter your keyword into the search field and select on search.
4. The missing mail will be visible.