Sounds like this was your fault, not the horse's fault.
When loose, some horses will go back home. They are without a leader and the safest thing they can think of for themselves is to go back home. Your horse didn't bolt and throw you. He didn't do anything wrong.
I'm not sure how you can break your neck if your shirt got caught on a branch. You would either be dragged off the horse by your shirt or your shirt would have torn...it wouldn't have broken your neck.
It sounds, from what you're describing, that you directed your horse into thick underbrush, got caught up in it, and are now complaining that your horse kept going without you. You directed it into thick underbrush...shouldn't have done that.
Chock it up to a lesson learned. Don't barrel into overgrown trails. Trail blaze slowly, and with a compass. Always carry a cell phone, and always tell someone that you will be out for the day. Travel on trails that have been CLEARED for riding. PAY ATTENTION to whats ahead. DUCK when you see a low branch.
Again, your horse didn't do anything wrong. It was all rider error. Next time, be more careful.