Prior to upgrading to Mavericks, I had a draft of an email I'd intended to send out later. Following updating, the draft was gone. Completely erased. Is Mavericks not saving drafts anywhere at all, much less in the appropriately-named Drafts folder?
I noticed this too. When composing a message after the auto save happened and I closed out of the message and chose 'do not save draft' the Drafts folder magically appeared.
I had a stack of drafts in my mailbox and all but 3 are now gone. I went to restore them from Time Machine but they only momentarily re-appeared and then disappeared again before I could copy them to somewhere else. I re-restored them twice with no luck. Pretty annoying "bug" if you ask me. I hope 10.9.1 turns up with a fix soon