If it is completely gone, then no, in my experience it won't grow back. I once looked after a rabbit that had several claws missing. If he isn't bleeding, just keep an eye on the healing. Once healed, he should be all fine.
I've had the same happen with my Agouti's and they grew back. I think when they were playing they hit the cage top that I had and I remember seeing Chica shake her foot. That was about two months ago and I do see a nail where it came out on her...
You really just have to wait and see. Also keep a close eye on it to make sure it doesn't develop an infection. If the gash is very big, you should take your rabbit into the vet to get checked.