A slutty day out.
Now, this next bit might be a little tricky. You are not allowed to go into the toilets/changing rooms - you must find somewhere secluded but not totally private.
Take out your buttplug - if you were smart enough to bring lube, you may use some, otherwise you can suck on it. Insert it inside yourself, so both your holes are nice and stuffed.
Walk to another location, and take out the panties.
Now you need to find somewhere like a bookshop, video store, even a sex shop. Somewhere that has a section aimed at 18+. You're going to hide your wet panties somewhere in this shop. Slip them between the pages of Fifty Shades of Grey, add them to display of porn, whatever (feel free to skip this part if you think you may get in trouble, or to leave them in the toilets instead).
All done? Now head back to the toilets.