Need Help! What could it be?

If a child has been throwing up, stands up and loses her balance, not herself, doesnt talk much just says yes, no, doesnt want to do any of her favorite things, no candy or ice cream, no toys doesnt want to go outside....she was taken to the doctor and they couldnt figure anything out and was told to bring her back tomorrow...they couldnt find anything wrong, only thing is she has a new tooth coming in (she's two). Parents are concerned and worried and wondering why she was just sent home with no answers.

Any thoughts