Of course, when you’ve chased down an idea, you’re usually ready for it – at least in the basics of having pen and paper, or a keyboard, or whatever method you prefer to record your writings by. I don’t know, human ingenuity on the topic of recording the written word is pretty extensive. Maybe you use granite and a set of chisels for your writing. (If you do, more power to you and I am very impressed – also, how do you edit?) Whichever method, if you were hunting an idea, you were prepared to write it.
When an idea chases you down, however, it can be far from such convenience to retain it for later use, much less express it coherently afterwards.