Most forums and many websites (like gmail) are able to save your post in a cookie as you type. If you navigate away by mistake, the post will be waiting for you if you go right back.
Does the billion dollar forum have that feature? I got so used to it I forgot this forum is so old... :/
Lol...this is overdue and the forum is old truly, I could remember when I suggested the
autosave function a while ago but nothing was done about it. This function is old with some sites too and it's not about BTT being old per se but the lack of a plan for such a function itself. The forum has tried for itself and I believe they are taking time sometimes to update some functions on it. But it needs more than that, the forum that will compete with the recent technology is deserving of the Bitcoin status as it is now.
Also about this issue of yours, I believe that it varies per browser and you might want to update your browser too. I use Chrome to surf Bitcointalk and when I mistakingly click on the back button and later click on the forward button, it retains my typed work. This also goes to when I mistakingly closed the browser or shut my laptop entirely. I always get back my typed work in these cases with my updated browser.
The only exception to this is when I refresh the page.