Quarter Inch Piece of Plastic

I have a notebook that I do my writing in. It's actually a journal, but I use it as a notebook. I've had it since 2007, and I tend to write short stories in it as well as this year's NaNo.

So as I'm flipping through it this morning to find my outline for the chapter I'm working on to check a detail, I come across a lined piece of paper that's folded and stuck inside. It's notebook paper—different from the paper that the journal uses.

Unfolding it, I realize it's my father's handwriting, and at first glance it appears to say, over and over and over again, filling the entirety of the paper, "hidden words." Upon closer inspection, however, the phrase, while taking up the majority of the paper, is not the only thing it says. Peppered throughout the "hidden words" are similar sounding phrases like "hide in words" or "had an urge" or "hymn a dirge," etc., but it's weird as hell.

I don't know how it got in there. I've never noticed it before. I rarely leave this book out in the open, though I have on occasion. I don't know if this was placed inside on purpose or what it might mean if it was. But it's really fucking weird, right?