I'm currently a Girl Scout Leader of 2 troops, Brownines & Juniors in one, and Cadettes & Seniors in the other. All my "girls" know and love this song. It brings tears to many of our eyes too.
We had also heard the story of the sick girl, in a wheelchair that watched the barges sailing up and down the river thru her window. We were not told where she was or which river. It was sad enough to know she was ill and wheelchair bound.
I remember singing it in Scouts in the early '60s & taught it to my adult daughters when they were in Scouts as I have now taught their 2 little sisters 14 & 11. We didn't sing a 3rd verse either, but I sure am enjoying picking up more verses for the more somber version. (We have several verses of the "camp" type ones that the girls like too. Funny how I also have the girls do the "original" version first like someone else mentioned. It's a "respect thing" for me.)

I'll keep checking you guys out to see if someone, somewhere comes up with the real thing. (But, I must admit, I'd be sad if it wasn't something like the sick child story.) Either way, it's a beautiful, melancholy song.
Sondra aka Nana