Disappearing email drafts

To date I have lost 5 email drafts in the past week.

1. I begin typing the subject and body of the email I intend to send.
2. Before I hit "send" I open my inbox to find a past email or search for something on my computer using Safari.
3. When I go to finish typing the original email, it has vanished.
4. It does not appear in my draft folder or trash - where is it going?
5. There are no open windows (which is how it used to function)

Please help - I am super frustrated. I attributed the first couple to operator error; I have lost at least five draft emails to date.

Thank you,

Malissa