while there is an automatic feature to save draft messages, I have never quite understood quite when it actually would do so
In my situation, I see drafts lost on a regular basis, and not only on GIO. I'm in a somewhat remote area with minimal options for internet access. I've managed to find utilities that will show a 'live' icon on my computer so that I know when access is lost (sort of like the modem lights of days gone by. ;>) At that point, I try to get back online so I don't waste a lot of time typing something that can't possibly get to the site where it could be included in a draft. Until the browser folks come up with a local draft cache (if that's even possible), there's not much that any site can do about it.