Voyager takes after the Apollo app in this regard, where if the app is closed while text is being edited, it'll bring back the unsaved draft, but it'll pop that into the next reply window you open, even if it is a different thread entirely.

Being able to reopen the same thread and resume editing would make it much easier if you're switching to another app to look up a reference or a link, and Voyager gets destroyed by the OS. It'd also help refresh your context if you can't remember what it was you were writing and why.