Well, YY, I had a sort of related thing happen to me a while back when doing a happy hour for a Masonic Retirement Community.   
I was setting up to do the music and went to the ladies' room for a pit stop beforehand, and when I came back and turned to pick up my guitar, one of the women discreetly called me aside and pointed out that my skirt was tucked into my pantyhose in back.   
(Fortunately, I was also wearing underwear, and the skirt was rather full, so I probably hadn't "mooned the Masons" too shockingly.

But another potential 'Mason-mooning' incident happened at the same Masonic home that same summer.   The women's restroom on the second floor had one of those windows that, for some reason, was placed very low to the ground. As I finished my 'service call' and stood up (pants around my ankles), I realized to my chagrin that, with that low window open, as it was, there was pretty much a direct eye-shot from the grounds of the courtyard below to my   backside.   (Whoever designed that loo should have been sued.)

Fortunately, as far as I could tell, no one had been in the courtyard below at the time.
But I couldn't help thinking that, if this sort of thing kept happening there, I would have to immortalize the occasions in a song such as "Merrily Mooning Masons On A Monday Morn."