depression/detachment/fear suddenly from a hyper dog

Just two days ago, my hyperactive minischnauzer transformed into this strange dog I don't know (and seems like she doesn't know me---our 8-9 year friendship does not seem to register with her anymore, she doesn't seem to have any particular affection for me).

Symptoms:
-sits awkwardly for hours on end looking at things like the floor in front of her or a blank wall 2 feet in front of her
-she acts nervous/timid/scared, especially around me in close quarters and in our house (in the car from the vet, she was fine but when we got home didn't want to get out---also just took her on a walk, and she was almost normal until we got home).
-won't eat/drink anything (even favorites like chicken, milk, etc)
-is in physical pain; vet could not diagnose where it was originating from

History:
The night before this all happened, my dog vomited in our bed.  There wasn't much vomit left when I woke up and first realized she vomited, so I guess she may have re-eaten that vomit.  The next day, my dog had a rectal temperature of 103, which I understand is slightly above normal for a 15lb dog.  The morning after she had diahreaa (but this might have been because at this point I was forcefeeding her chicken which doesn't always sit well with her stomach).  I took her to the vet later on this day.  The vet treated her for acute gastrinal intestine bacterial infection, but nothing on the weird behavior.

Shots in the Dark Possibilities:
-Prior to this, my dog was scared of our propane fireplace (the fumes themselves make her hide in a backroom).  Our furnace has been out, so I have been using the fireplace and an electric wall heater to keep warm.  I haven't used it today however, and my dog is still as odd as ever.

-2 days ago, I let my dog out in the backyard late at night.  My sick dog seemed to chase something, but I don't think she caught it.  Looking around in the yard today, in that same area I see some kind of animal hole.

[Cliff Redford, DVM]

Interesting case. I do not believe this stems from some of the past fears your dog has had. It sounds like your dog was hallucinating a little for hours at end and this actually can happen in dogs and strange as it sounds can be due to seizures. Not all seizures are your typical grande mal type - some can take on very prolonged forms of behavioral changes. If it continues to happen then asking your vet for a referral to an internal medicine specialist, or a neurologist is recommended.

[ihavezippers]

Just to update, my dog now has her nose to the ground and is rocking back and forth like a junkie.  She did this for 10 minutes, except when I called her name.

[LivingLife19]

By any chance do you think she could have Parvo? Smaller dogs tend to get this, and it will cause them to do all the things you have mentioned. But you also mentioned her chasing an animal? Make sure she has no bite marks our any open wounds if so she can have an infection or something else if she could have been bitten. The thing that scares me about this is that you said she vomited and had diarrhea, a number of things can cause that and some of those things can be fatal to a dog, If she is still like this I would recommend taking you dog to an animal hospital so you can figure out whats wrong with her, it may not be anything serious, it can be stress from being scared of something but when it comes to a dog acting like that, I would be extra careful with how long you wait! I hope everything works out for you, let me know how everything goes. Good luck!