When you're working on a Blast, the Blast Editor does NOT autosave. This means, if you exit the Blast Editor without saving your work manually, you will lose it.
Any edit to your Blast will need to be saved! To save your Blast as a draft, click Save as Draft (located above the Blast Editor).
Please Note: There are not multiple saved versions of a Blast. This means ONLY the most recently saved Draft will be available to you.
To learn more about how to send you Blast, check out this article.