After reaching the end of the narrative, and it becoming obvious there was '1 more' to find, I thought it was fairly obvious what to do. After that, realizing there was '1 more' still... yeah I was stumped. But then the next morning, while driving the car, it suddenly came to me to try out something out of the box, couldn't wait to get in front of a computer to try it out... and it worked...
I think making it more obvious would be a detriment to being able to figure out something more out of the box like this. Maybe, if one minor change was made... it would be to make the words 'rolling thunder' to 'rolling thunderclap'. But honestly that wasn't part of what made me think of what to do.