Left my dog with a sitter for the first time and now he's different?

Our 6 month old Husky puppy, stayed with a sitter for the whole day, 8 am to 9:30 pm. When I first dropped him off in the morning he was happy, talkative, loud, wagging his tail. Caregiver sent me pictures of him during the day about two-three times. It was a hot day, in the 90s...The sitter said he drank lots of water and ate when he was hungry. Anyways fast forward, I came to pick him up with my fiance and he was a different dog. He did not greet me with a bark(yelling at me) like he normally does when I leave him at the groomers .. he was quiet, sad, no panting, mouth was closed. He even had a nasty stench one he did not have when I dropped him off. We drove home and mid driving he vomited liquid in the car. He was completely not himself.. We came home, he drank a bit more water and then instantly vomited everything back up. After he went to lay down and did not get up for nothing.. not the door when someone came like normal, not to the kitchen when the fridge opens like normally. He just laid there.. like he was in some sort of pain. Following morning we took him to the ER because now he vomited and had diarrhea. They advised to start to give him medication for a parasite even tho blood panels came back normal. He also got anti-neaouse injection, but later that night I gave him a tsp of wet dog food and he ended up throwing it back up. Next morning he seemed to be somewhat better, tail was wagging, moving around, reacting to other stimulus like kitchen door, outside door, bell. But he still isn't barking, talking, is moving at a slower pace and keeps laying down sleeping and not interested in any of his toys.. I should probably mention I am feeding him small amounts and only giving him small amounts of water to prevent anymore vomiting. I guess my question is .. did anyone experience this before? I should mention this is the first time we've left him with someone we did not know.. for more then 12 hours. Sitter expressed he didn't have anything out of the ordinary..