I don’t know how correctly I understood your text, but on my laptop, when I write a post, press the back button, and then click again on the page to print the post, everything is saved. Maybe the problem lies when using mobile gadgets. I deliberately tried to do this, but maybe this happens after a pause.
I am using Chrome to surf Bitcointalk on my Windows and the condition is pretty much the same with my device too there is no need to click preview/draft just to get what we wrote when we click backward but the condition is different when we use reload/refresh feature.
Also in my Android too the situation is same but where we most likely will refresh the page while swiping down and all the text written will be gone but its unlikely to happen with PC.