BCP401 - AIR
Yes this cap certainly had AIR. It must have taken a deep breath and retreated into its own personal swimming pool when it saw me coming. I felt the cap's circular outline with the screwdriver I was carrying, so I know it was there, but since it was under water there's no way for me to actually prove that. I tried waiting it out (to see if would run out of AIR), but that didn't work. I even shouted "Everyone out of the pool!!" Nothing. This was one stubborn cap. Beaten, I returned to the car, vowing to come back when the water has receded and the cap will be forced to come out and play.