LOST COMPOSED EMAIL REPLY

I was composing a reply to an email on my Mac laptop. I wrote a lengthy email response and needed to check calendar for dates in reference to a question from sender of the email. I use my iPhone to check dates on the calendar. There was a pop up about an email draft to save or delete. I was thinking it was probably a blank draft and deleted it. I didn't think to read and see for sure what the draft was. I just assumed it was a blank draft in my iPhone email. Then I went back to complete and send the composed email on my Mac, only to discover it was GONE!! Oh, no, no, no, NO! What happen and how did it happen? My assumption about the iPhone draft, now meant the connection to the email I was composing on my Mac laptop!! So I need specific help to learn how to get that long email back, if at all possible. Otherwise, I'll have to try and remember and reconstruct the best I can the lost email. Any help from the community?