Now I'm curious how you managed to recover. I only know enough of my way around a shell to be dangerous and I'd be SoL if I ended up in this situation.
Recovery disk, then either copy the disk's copy of bash (if it doesn't depend on a later glibc version), copy another shell to /bin/bash (as the system probably doesn't depend on bash-specific commands to boot), chroot and use the package manager, or use the package manager with an explicit sysroot (e.g. pacman --sysroot). The first two steps are very easy compared to the latter two, but should be followed by a reinstallation of the package that provides bash.
