Brian,
I remember that day very well. Before we backed up, those of us in the cab personally checked the alighnment of the switch because it was hard to see from the cab and it is an unusual stub switch. As we slowly backed up an unseen visitor (with good intentions) threw the switch thinking it was not aligned properly. No one in the cab was notified. As a result, the tender dove into the ballast, It was a good lesson that unless someone is part of a crew, they must not mess with operations.
The only damage was to the white walls of the tender wheels, and a few hours of getting the tender back up on the rails. The visitor was mortified at what he had done.