The same happened to me once, but no one saw as it was just the back and my hair was covering the front part of my body. Still it is very scary!
No turkish costumes with small back straps for me anymore!
I must confess that I do wonder about any problems with "the boys" and their special accoutrements during all that hip shaking, but am too shy and blushing to ask a Veiled Male what he wears under his bedlah.