Quoting Peter Olson (peabo@???):

> Turns out, I had managed to screw up my partition table. So Grub
> would never in a million years be able to boot anything off that disk.
> I found this out during reinstallation when I was presented with a
> partition table different from what I expected.

It's late for this now, but if you _had_ known that the problem was the
partition table, you could have fixed it using TestDisk or gpart
http://www.cgsecurity.org/wiki/TestDisk
https://en.wikipedia.org/wiki/Gpart

(I mention this mostly to spread knowledge of two useful tools.)

> Nevertheless, my complaint is that Grub is not helpful in these
> circumstances, lacking even a help command at its prompt. You really
> need impeccable Grub-fu or another computer with net access.

Very true.