Please don't worry too much. If your bunny wasseriously sick, it would not be hopping about, instead it would besitting very still and bunched up, not wanting petted or touched, mayhave it's eyes closed or partially closed and could be making loudcrunching noises with it's teeth. It would not want it's favourite food(or any food) or a drink. It's ears could also be cold but I think ifyou pet your bun's ears they will warm up.
Good luck