First, greens and vegetables aren’t bad for rabbits – what do you think rabbits eat in the wild? They just should be introduced one at a time and progressively if your rabbit comes from a place where rabbits aren’t kept correctly (aka pet shops) and don’t have access to greens. As an adult, vegetables (especially leafy greens) will be the second thing your rabbit eats after hay.
Next, don’t panic. Orchids aren’t poisonous and as I said, greens aren’t bad for rabbits. Moreover if your rabbit had a reaction to it, he would probably have diarrhea. Poops getting smaller can come from the stress of being moved – most rabbits don’t like it and next time, it might be best to find someone who can come to your house rather than moving the rabbit for just 24h. As long as the rabbit is pooping and eating, I would just keep an eye on him and offer lots of hay like you already did. It can take a few days to go back to normal. Then, if it’s not better you might need to phone a vet. But I really wouldn’t risk stressing him even more as long as it’s just a slight slowing of the guts.