It’s not that I’d forget such details, but more so that I’d forget to remember them. They’re recorded just fine in my brain but there’s no prompt to bring them back to mind. So the notebook entry is the prompt. (More recently, I’ve been trying to carry my tiny camera … one click captures a visual detail so much faster than writing down all those descriptive words. But cameras tend to get people’s notice; the notebook is covert.)
I once listened, for example, to two people having a one-sided conversation. After a time, it struck me how many ways a person can lob dialogue back to the other party without really participating:
I wrote them down to use, someday.