Several years ago, when I was very new to carrying, my first pistol was a Taurus PT145... and I had no holster (I know, I know...). Anyways, on one particular trip to the local auto parts store I was just finishing up paying for my purchase when I felt my gun moving downward from where it was tucked into my waist-band. I tried to surreptitiously secure it as I reinserted my wallet into my back pocket, but I was too late.
Thud... clack!
The pistol slid all the way down the inside of my right pants leg and was laying next to my foot.
The cashier leaned over the counter to see what happened as I gaped stupidly at the ground... nobody said anything as I scooped it up and tucked it into my front pocket and sheepishly retreated out the door.
On the way home I stopped at the local outdoorsy shop in town and bought a cheap Uncle Mikes IWB holster (which didn't get used long either, but that's another story).
It's funny now.