If you'd asked me I would have said this could never happen! Anyway, it became a bit of a bother to get it out because although I could grip part of the rim, it was too slippery to pull out easily. In the end I just yanked it out fully open, which was pretty uncomfortable.
Still, it hasn't put me off completely and I'm wearing the GreenCup as I type this. So that's a new experience for me - and a new one for the board? Or has anyone else been suprised at the "critical moment"?