I've had my bra catch on the horn as well, but not dismounting. I was on a greenish mare out on the trail with a bunch of others and we were tackling a fairly steep climb. She slipped a little and panicked, launching herself upwards and sideways over a ledge to the top of the hill instead of following the curving path. Some how I doubled over on her back and hooked my bra, which was great fun trying to unhook while she proceed to continue up the rest of the hill at a jarring trot. Of course I was in the front.
There is another one that I laughed pretty hard at though. I was taking English lessons and the horse I normally ride had an accident and was out of commission for a few weeks. So they put me on the beginner's pony. A little shetlandX gelding, who I justify this with by the fact that he hadn't been out for a few weeks a
Anyways I'm walking along, not paying attention to him as the instructor is focusing on the other two riders in the lesson, who are beginners. So I'm feeling pretty good at riding, I have about 5 years of riding experience at this point, on beginner's pony with two other beginners.
Murphy's horse law at this point? Yes. Out of no where he ducks and bucks and I land on my butt, right in front him still holding the reins like I'm still riding. I was laughing so hard I couldn't answer the instructor and she made everyone stop and freaked out that I was hurt.