It's been that way for a few months now. Here's the solution. After you login again, your post disappears. However, slowly and carefully hit the back arrow button. I can't remember how many times you need to hit it (probably 4 or 5 times). It eventually will make your post reappear, but you have to allow a few seconds after each time you hit the back arrow button to let the entire page reload. If you hit it too many times, your post will be gone for good.
I purposely took a long time typing this post which required me to login again. It may vary how many times you have to hit the back arrow button to make your post reappear. It happens to me all the time, but I constantly edit and preview some of my longer posts until I get the wording just right.