Well, it's only been a day, I'd give him a couple more. I think he missed you, he was scared and unsure a the vet's, he was stressed because of that situation and the mite situation, and he's mad at you for leaving him at the vet's. You probably realize that animals do not like change. He just needs to realize that he's home, he's safe, and relax. It could take a few days for him to get comfortable again.
When I came home to visit after being away at college longer than I ever had been away from home before, my dog Lady was p***ed at me! She made it a point to ignore me for several hours until she decided she had "punished me" enough and jumped on me happily. I swear, nothing is more surreal than your dog being spiteful and actively ignoring you. (She was happy to see my mother, who had picked me up.)
Also, Loki, my kitty, had only been with me for 10 days when we moved. My Mom, sister, and stepniece were helping me move into the actual apartment. I was riding in the van with my Mom, and had my sister and niece take Loki since they were taking a car. There was a really bad ice storm, and my Mom and I stupidly decided to try to make another trip (2 hours away) to get some more of my stuff, leaving my sister and niece at my apartment with Loki. Several hours later we made it back to my apartment alive, and Loki was not happy to see me! My niece was asleep, and so my sister, Mom, and I and were talking in the bedroom, and Loki was in there with us. He kept ignoring me and was acting cold toward me, and I thought he was going to hate me forever! When my sister got up to go to bed in the living room, Loki reached out quickly and grabbed her arm. It was very sweet, but I was a little freaked out because I was worried that all of a sudden he got attached to my sister (literally!) and liked her more! After everybody left and it was just me and Loki, it still took him time to warm back up to me, but after awhile he was fine. And it turned out he loves his Mommy more than his Aunt!
If your kitty still isn't back to normal in a week, perhaps, I'd call your vet and ask him for some tips, but don't just hop in the car with your kitty and go there! Just call first, and see if it's necessary to go in. You don't want to upset your kitty-cat more! Good luck!