After some tag-team with Simon, we discovered that he'd probably installed in expert mode from d-i and intentionally selected a MODULES=dep setup, which was why he wasn't getting hid modules in his initrd. After we backed that out, we tested the new initramfs-tools on both precise and quantal kernels and his cryptsetup password prompts were accessible and working for him.
After some tag-team with Simon, we discovered that he'd probably installed in expert mode from d-i and intentionally selected a MODULES=dep setup, which was why he wasn't getting hid modules in his initrd. After we backed that out, we tested the new initramfs-tools on both precise and quantal kernels and his cryptsetup password prompts were accessible and working for him.