This is a serious problem. I started to create a post for my community. It's not easy, because some features are missing (eg sending URL to OpenBook and/or gathering intros from news/web pages). So I need to collect some data for the article. URL, picture, text to cite. For that I switch between Chrome and the OpenBook app. In this workflow the started article get lost. I'm back in the community overview and my work is lost.
This behavior is IMHO a bug. As an additional feature I would suggest a draft area. Every leave from the App should save/update an article to a draft area (not only for a single post). This is maybe a good fix for the problem.
Anyway, I love OpenBook and your work on it.