Yep - I have seen some strange effects after a raid5 rebuild but in this case I dont know the state of the raid - as soon as I found out that there is no way to mount the VMFS or fix the damage I booted into Linux and started carving out the vmdks.
Wonder if I ever have the time to investigate this case in more details .... soon after I started to work on the first lost VMFS-volume two other hosts followed.
It is a pity that we do not even know if a repair of this type of damage is possible.
There is documentation for force-mounts when the LUN is detected as snapshot but there is nothing as far as I know on force mounting VMFS that lost the LVM magic number. Looks like the vmdks are still there as I can carve them out the hard way - well at least the thick flat.vmdks.