Wet girl,
That is an absolutely beautiful idea. I love the fact that it is a naturally occurring event which then looks like it has caught the sub unprepared. It brings on a level of embarrassment and humiliation by highlighting the sub's inability to cope with, or plan for, a basic bodily function.
Also, without directly exposing her privates, it focuses the attention of anyone who notices directly on her pussy, and on her unfortunate condition. Certainly the larger the accident the more people will notice. Likely some stranger will alert her to the issue, and she will have to interact with them, displaying an appropriate level if panic and embarrassment, admitting that she is not entirely prepared for what her body is suddenly doing. The great thing about this is that she can quickly exit the store as if she going to take care if it, and then simply walk into the next store and resume her act of innocent and oblivious girl.
I would love to take you out for a long day of shopping. I can't decide if I'd rather have you wear a short skirt or some white shorts. In either case there would be no panties, so it's just a matter of displaying your personal mess smearing along your inner thighs, or blooming as a patch stain in the crotch of your pants.
Can you tell us about a time when you have discovered this accident while in public? Was it a true surprise or were you being instructed by your Dom? How do you think you would feel or respond to this happening based in the two outfits I mentioned?
Part of my fascination with this scenario is that I would look forward to licking you clean when we finally got home that night after a full day out and about, shopping, dining, dancing, and drinking.