What feeling you have when you get spontaneous activation?

Is it same feeling like when you remember something from normal reading?

For example, I was read one linux book few months ago, before I was start PR. I never PR that book.
It's very good book about GUI - KDE, GNOME, etc.
Now when I work on KDE and I need to know/remember something (from that book), I just know that this information come from that book and I know approximately where is it in the book (in beginning, in the middle, or end part). I don't know exactly chapter or page number, just approximately.

Does spontaneous activation work like this, or you JUST get/know information, but you don't know from where it comes?
Like driving a bike or swimming, you just know you can do that and you just do it.

Or something else happen?