KVM: old working .img files no longer seen by virsh list cmd: how to recover?

Hi guys, setup 4 KVM VMs back in August.
Haven't played with them in a while, want to revisit/get myself current again.

 ls -lh  /var/lib/libvirt/images
total 8.7G
drwx------. 2 root root 16K Aug  5 11:01 lost+found
-rw-------. 1 root root 15G Aug 16 22:07 vm1.img
-rw-------. 1 root root 15G Aug 16 22:07 vm2.img
-rw-------. 1 root root 15G Aug 16 22:07 vm3.img
-rw-------. 1 root root 12G Aug 18 17:12 vm4.img

 ls -lh  /var/lib/libvirt/images
total 8.7G
drwx------. 2 root root 16K Aug  5 11:01 lost+found
-rw-------. 1 root root 15G Aug 16 22:07 vm1.img
-rw-------. 1 root root 15G Aug 16 22:07 vm2.img
-rw-------. 1 root root 15G Aug 16 22:07 vm3.img
-rw-------. 1 root root 12G Aug 18 17:12 vm4.img

 chkconfig --list|grep virt
libvirt-guests 	0:off	1:off	2:on	3:on	4:on	5:on	6:off
libvirtd       	0:off	1:off	2:off	3:on	4:on	5:on	6:off

 service libvirtd status
libvirtd (pid  6929) is running...

 service libvirt-guests status
started

 virsh list --all
 Id    Name                           State
----------------------------------------------------

ie everything is up and running, but virsh can't see the imgs anymore ...

I'd really like to re-activate the current images instead of re-creating.
in any case, I'm sure I'd learn a lot by solving this problem.


===================================================================================
UPDATED:
ok it appears when I got a new m/board (back then sometime) to get extra RAM, forgot to check Virtualisation was enabled in BIOS... It was 'Disabled' .. sigh
Rebooted, Enabled Virtualisation in BIOS et viola

Actually, same qn is still valid for vm4. ie

virsh list --all
 Id    Name                           State
----------------------------------------------------
 1     vm1                            running
 2     vm2                            running
 3     vm3                            running

so, 3 out of 4 are good to go.
Any ideas how I can 'debug' / enable / activate vm4 ?


=================================================================================

LAST Update
ok, used http://linux.dell.com/files/whitepap..._made_easy.pdf Section 2.1 to debug.
Turns out the 'disk' inside vm4 is totally blank / not partitioned.
Can't remember why; think I'll just delete vm4.

Hope these notes will be of some use to later readers

For me, sometimes virsh list --all doesn't actually show all the defined VMs. Is it an option for you to run virt-manager on the host? Or run it on another host (e.g. your workstation) and connect to libvirt on the server?

If you can't find the vm4 defined, then I suppose you can just define it as a new VM and add the existing disk image as a disk drive.