Stage fright. Always make sure you are busting for a piss when in a busy pub else you have to go through the shame of standing there in silence while others splash away and smirk to themselves.
I remember working opposite the blackbird leys pub in oxford many years ago and was bursting for a piss , so having no other choice ran over to use the facilities , i was surrounded by about 4 big black guys at the urinals . And you've pretty much described the outcome above .