I would also try the horse out many times before you get a new one. Also show up to see the horse at times that they aren't expecting you so that you will know for sure that the horse is not drugged or something.
Really sorry this happened to you with your first horse. That can really hurt your confidence but I wouldn't let it stop you. Find a horse that has good manners and will not be dangerous. I also would advise you get some lessons. They really help to at least give you the basics.