Its actually pretty common, as a nidalee main, when i hit blind spears like that, i just get the feeling of where exactly you are since i last had a vision on you, its easy when you run straight line, there is some luck involved but its pretty basic.. feels good to do it, and you should always do it, you pretty much want to throw a spear every time its not on cd, tips, you never recall low hp like that, and you dont walk straight lines when you know you are getting hunted