First, "init s" is not very safe on HP-UX. I always use the shutdown command, no exceptions ever. Still I am a little surprised that it did this much damage.
ISL is a program that resides in the LIF area. If PDC cannot read the LIF area, it cannot find the ISL program. It is possible to render the disk bootable again. You will need a support CD and and Support Media User's Guide to go with it. The repair procedure is documented in the
HP-UX System Administration Tasks manual. In the "Solving LMV Problems" chapter, the first procedure is "Booting When LVM Data Structures Are Lost". You will need to follow this procedure to recover. The Task Manual is online at HP's web site...
here is a link to the HP-UX 10.x version. Search for the 11.0 version if that's what you're using. I couldn't find the Support Media User's Guide online, but I guess it's useless without the support CD.
You can get the disk to boot if you follow the above instructions, but I would still be concerned about other damage to the disk. Re-installing might make sense. It's a very good thing that Rado1x advised you to perform a backup.