It seems there is a bug where these blank scrolls lose the content text written in them, either after resets or if the holder drops their bag, be it from subdue or death.
Only their topic remains intact, but the content text has gained the default "This is a blank scroll of the kind casters use..."
edit: It also seems they cannot be written on anymore, they are still tagged as already used. "Cannot be written on further"
It's the same with books, yeah, there's been a few threads about this, but I suppose it's just a mechanic that can't be fixed or is intentional. =[