3 drives fell out of Raid6 mdadm - rebuilding?

Information is taken from this article, see if it is of any help: http://www.linuxjournal.com/article/8874

pvscan shows that there are LVM physical volumes present, but LVM volume group is not necessarily active. See the output of vgdisplay, should be something like

--- Volume group ---
VG Name              zeus
System ID
Format               lvm2
[...]

If the zeus volume group does not show, you might need to make it available with vgchange zeus -a y. Then, check thet output of lvdisplay. This should output each logical volume in the system:

--- Logical volume ---
LV Name                /dev/zeus/volume_name
VG Name                zeus
LV Status              available
[etc...]

And you should be able to mount the desired volume with mount /dev/zeus/volume_name /mnt/target.