This is a glitch I have passed on to the coders and have brought up more than half a dozen times over the course of a year or more.
I don't know what the problem is with getting it fixed other than it can't be duplicated, therefore the reason for the glitch can't be found. I would suggest reviving the pet ASAP so that you do not lose the name if it is important to you. I do know that once a pet has died in this manner, it will not happen to the same pet again. It only affects pets with a certain date of birth, and I believe that date is the same as the release date of V2.
If you have pets in your graveyard that still have an amount of hunger, staff can provide you with a resurrection potion.
In some cases, staff can help you reclaim a name that was lost to this glitch if someone else has it, but we have to find proof that the name belonged to you first in order to be able to do this.
You will need to open a Support Ticket if you need a resurrection potion or help reclaiming a name, though. Don't post about it in the forums.