in shock?

hello! Im still new to the bun world. I’ve had him about a year and half.
Today I went outside and discovered my bunny was out of his cage roaming around my dogs. So instinctively I grabbed him. He started breathing heavily , painting and all. He didn’t calm down for about an hour and a half , He hid in the corner and I brought him into a safe place and wrapped him in a blanket. I got him his favorite veggies and gave him water through a syringe so he seems to be doing ok. He’s not hunkering down a lot , he’s moving around but laying completely flat and rubbing on me. I’m just worried. Any tips for keeping an eye on him ?

If he was panting, that means he was dangerously overheating. Him laying completely flat is him trying to cool off. If he is still acting lethargic, panting, or having any other abnormal worrying signs of behavior, it's probably best to get him to an experienced rabbit vet.

If he seems to be doing better and is no longer panting, I would just continue to keep him in a cool environment and give him other ways to help keep him cool if he needs to. I would also feel his ears and see if they are still feeling hot.
https://myhouserabbit.com/rabbit-health/recognizing-heat-stroke-in-your-pet-rabbit/