There may have been many things that caused the hole, but there is a possibility that the bunny was shot by someone playing Elmer Fudd, and it got away. If you can get it to a vet who works on wild animals (without being bitten), great. If not, there is a good chance that the bunny will recover on its own. Keep an eye on it.
the best thing to do is take it to a vet immediately, it may get infected and become worse
A small amount of dead dryed grass possibly shredded paper or newspaper or a small amount of the stuff you buy at the store to put on the bottom of a hamster or gerbil cage but not so much of anything it adds to much pressure on the rabbit or can suffocate it.
A pet store?
you can go to the store and they would know if its a small one or an adult and they would tell them there birth I would check out the American Rabbit Breeders Association. Check the link for their website.
Borders
Probably a special milk formula specifically designed for adolescent bunnies you can most likely find a better answer from a veterinarian that specializes in small animals, or you can also find a better answer from a pet store sales associate also specializing in small animals. If you are trying to wean your bunny off of milk, you should try pureeing a mix of vegetables and blend the pureed veggie mix with the small animal milk formula. Also there is bagged bunny food made by Kaytee you can find it at your local pet store make sure your bunny has teeth before you try this. Your bunny has to be completely weaned before it can eat adult bunny food. DO NOT RUSH OR FORCE THIS PROCESS OF CHANGE IN DIET!!! I will try to find milks and formulas that are acceptable for a bunny and then I will improve your answer.
walmart
A breeder, a pet store, a shelter(recommended).
Pet store. The wild. Depends.
You should store it in a stable cupboard on a high shelf, this prevents small children get hold of the items.
A grown bunny will usually cost 5$-$40 from a pet store. The cage will cost a lot though!
You could get one at a store with Halloween costumes or order it from a Halloween store online.
At any pet store=p