I thought about that also especially after hearing that Avila lured/conned Samantha with a "dog" story. It should have been taken and examined for insect activity or at least photographed for evidence and hair etc. preserved as same as almost all items at the crime site.
How interesting would it have been if it showed the dog was at the site exactly as long as DVD was?
I wonder if the dog could have been used to cover up the possibility of someone discovering the smell of DVD? So someone could say, "Yeah, what is that smell? Oh no! Great, a dog died in here, must have pushed the door open and got locked in here."
Nahhh, now I'm giving these people too much credit, although an experianced and VERY dangerous serial killer would think this way to avoid detection.
Bottom line yes. Every bit of possible evidence should have been collected and properly processed/digitally photographed at least.
Was an autopsy performed on the dog? Were toxicology tests ever performed on Danielle?