This is actually a no brainer, many times I have accidentally tapped on my mousepad while typing and took the focus away from a textarea then noticed a typo and

This is actually a no brainer, many times I have accidentally tapped on my mousepad while typing and took the focus away from a textarea then noticed a typo and tried to delete it and baaam you're no longer on that page and possibly all the text you typed has gone into the abyss.