I don't think this should keep making you still scratch your bald head, like last I used PC I mistakenly select a text on this environment and all what did lost I had to go and use my undo and everything Popup back as previous. Again, another thing you should do is to keep previewing your post whenever you typed in some words this would help you alot. You should be that used to the entire system how it operates by now.
I fell victim of this particular frustrating event too many times that I actually got acostomed to making use of my notepad before transferring it to the forum especially if it's a bulky post I'm trying to compile. As a designer sometimes you forget you can't actually use the undo button every time lol...
After I learnt my lesson I become used to regularly preview my post at all times before I do other task or maybe even minimize my browser because sometimes I usually close my active tabs without me having to submit my post.
And Yes, if you aren't that smart enough working on the window you wouldn't know you exist the window so quickly or even lose all your post.