If you try to backtrack the way you came, the elevator you descended in explodes and there's a fun little "well... crap" music queue.

: I remember spending some time on that trick, and finding it a bit… er…
: tricky. I don't seem to've covered it on my site yet. Dang. That's another
: item for my huge backlog.

I believe I learned it from RC Master's guides for the original CEA. The only real trick is avoiding the rocket Flood, both with your banshee going down the tunnel, and in case any survive when you go back to get the Ghost. There's also some checkpoint stuff you can blow past and accidentally glitch yourself out of progress, but if I can do it I imagine you shouldn't have too much of an issue :)

: Sudden random thought. Did Scurty name himself that way in honour of the
: security substation? I mean, just remove a few vowels…

I dunno. Couldn't find anything about his name online.