Awww thats too bad.

For future reference if you ever see another, when rabbits begin to live independantly and leave their mother, they still look like babies. By the time they look like a miniature adult and are able to hop around like a normal rabbit, they are eating and living just fine on their own. It's probably safe to say that the rabbit you found was fully weaned and on it's own but just got an unlucky encounter with a hawk, cat, dog or other predatory animal.