How big is the baby?
I used to breed show quality Lionhead rabbits, and I hate to be the bearer of bad news, but it is next to impossible to hand feed a baby rabbit. They don't take to a bottle well and it is hard to find an appropriate formula.
The best thing to do would be to see if there is a local breeder in your area that has a nursing doe, and see if she will accept and foster the baby. Otherwise, I'm afraid the little one will not make it.