Tornado was hauling a tour last December when the train was used to convey some "normal" passengers who were stranded due to lack of their usual 3rd rail emus in the snow and ice, report here .
I also seem to recollect Leander rescuing a freight on the S&C in the late 1970s / early 1980s, perhaps somebody can remember the details.
Well that was a pretty daft move. Why not just allow the 31 to take the train off the mainline? Surely that would've saved a lot of trouble.
Aviemore's got bi-directional mainline platforms. I don't see why the 31 couldn't have been allowed to tow the failed train into one of the platforms, allowing passenger services to use the other platform. Unless, of course, the freight was too long and still overlapped the loop.