This is the act of cock blocking
yourself. This can be done for a variety of reasons including, but not limited to; fidelity requirements, embarrassment, awkwardness, sobering up in the nick of time, etc. Doesn't happen very often and typically results in feelings of confusion and possibly guilt.
The hottest chick ever hit on me last night at the bar, but with my wife home with the kids and no one else to save me, I masterblocked by donning a helmet and a hula hoop, while running out the door screaming like a little girl.