Looks like the chum did not have to lose any data.
Wiping out the MBR and the next 63 blocks apparently only wiped out grub stage1, partition table, and part of the lvm config data.
I get to try to do a lvm 'recovery' at his expense now but this is my first time...has anybody ever tried restoring lvm config data back to the md/pv device?
Cheers,
Christopher