Who caught you out (wife, bird) and since you had no excuse what happened after?
Wife and possibly others but all I heard at the time was something like "What's that red stuff around your mouth? It looks like..." and she stopped there. I knew what it was straight away and instinctively bolted out of the room and quickly wiped it off. Nobody got a second look. I came back shortly with a lame "dunno what that was" and crossed my fingers. The had a day of the silent treatment but since the evidence was removed quickly there could be no further questioning. Things have been a bit warm and cold since so I think I'm under observation/surveillance now. She's not stupid but in my normal persona I don't even talk to opposite sex so it's a massive stretch for her to conclude that I've been with another women.
I'm usually very meticulous in all aspects work and personal life. For this punt I broke all my own rules and operating procedures. The WG I visited was amazing though and must have, er, cast a spell on me or something like that.