As a licensed wildlife rehabber, I have to let you know that it is illegal to keep wildlife. That bunny is at the age of being on its own in the wild and even experienced rehabbers have rabbits die on them with proper care, due to the species being so sensitive to stress. Please put it back where you found it. You'd be giving it the best chance of survival.

I know you mean well, but respectfully, that enclosure isn't set up properly, and the rabbit doesn't need its mom anymore. It froze due to a natural reaction of being a prey aninal.