I feel like since it had only been an hour, I would have waited longer to see if he would eat. I know after taking my rabbit to the vet, she acts very sad and grumpy after coming home, and usually doesnt eat her full normal amount the next day. It takes time for her to de-stress.
I think you should keep the cone on and wait for a few hours to see if he eats/drinks. He may just need time to get adjusted to it.
If you do take the cone on be very careful and watch, make sure he doesn’t rub at it.
It’s a completely different case, but today a bird came into the hospital. He was supposed to wear a cone when he went home from his previous appointment, but for whatever reason the owner decided to take the cone off without letting the vet know. He ended being able to reach the closed wound he had and chewed it open and then chewed into himself. The purpose of the cone was to prevent this from happening, we’re not sure why the owner removed the cone.