I used to keep my dead African Snakehead in the freezer. It was the largest tropical fish I ever owned (about 27 inches long), and when it died suddenly, I was heartbroken. I’d raised him from a 2 inch long minnow. I finally got rid of it after a couple years. Weird? yes. Creepy? probably, anyone else’s business? Nope. I don’t see any point in your concern, unless this person gets it out and talks to it, or is somehow in danger of becoming infected with some nasty form of bacteria. It may simply be a symptom of grief and not being able to let go. Unless this person is in danger from the deceased pet, I really think you should just let it go. Probably isn’t anything to get in an uproar about.