I have certainly heard of people being charged with various crimes against police dogs. From what they said, the dog was considered a police officer. Harming the dog in any way was considered the same as any other police officer. I can't give you sources but all were TV and radio news programs.
We had a case here locally a couple years ago where a police officer shot his next door neighbor's dog because it kept coming into his yard. This was a small lap dog, there was no physical threat and the incident occured in a housing tract, not a rural area. The community was ready to lynch this guy. I know that formal charges were considered but I don't know the outcome, I don't pay a lot of attention to the "news".
As was already mentioned, I can't imagine someone forgetting about this dog. I have spoken to police K9 officers several times and I know these dogs basically never leave their side. They take them home etc. I know our arson dog never leaves the side of the arson investigator that it is assigned to from early puppyhood till the time it retires. They pick the dog up at I believe Quntico when it is about 6-7 weeks old and go through a training program that lasts for several months. They are never apart again. Our arson dog can't even be fed by anyone else. The officer carries a belt pouch of food at all times. Throughout the day he takes out an eyedropper of an accelerant and puts a drop somewhere out of sight of the dog. The dog has to scent the accelerant in order to be fed. This goes on all day and the dog never, ever eats any other way. It doesn't even know what a food bowl is. I would think that anyone with the intelligence of a house fly would at some point realize something wasn't quite right. He never had to let the dog out, clean up any crap, feed it or whatever; and he never noticed this ? And he should be allowed to have a gun and I shouldn't ?