I guess that even when your / is in an LV, it still has to be (or most probably will be) contiguous on the disk? This would mean that you could handforge a partition table entry that maps exactly the root file system. The size does not even matter (make it the rest of the disk), as long as the start sector is allright. Such a partition table entry would allow you to mount the /, even though it is in an LV.
If you want a good set of recovery tools, download an ISO image of the LinuxCare bootable business card (http://www.linuxcare.com/bootable_cd) and burn it on a CD. You then have at least a serious amount of tools to help you in the repair.
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