My coworker returned the shoulder-pad Gap pants for me without incident.
I waited outside, leaning against the corner of the building, trying to read a paper nonchalantly. I was too nervous that not only that the pads, but my own anxiety, would be palpable. I was sure that if I went in with her I would blush inappropriately, or stammer, or otherwise draw attention to the transgression.
My coworker had no such problem. She says that the trick is small talk. She said the cashier actually folded that pants a couple of times, perhaps feeling something odd, perhaps absentmindedly.
I lost a couple of dollars to mark-downs, but the pants should be back on the shelves by now, or at least on the clearance rack.