Once when at Dreamation, I was in a game of Lacuna ran by Jard Sorensen. Midway thru the game he got a phone call and had to leave, then Thor Olavsrud sat down and continued the game.. Having known Thor, and that Jard is a trickster, I didn't miss a beat and when along with it. However, I wonder if this trick from the New York Times post on Science of Illusion, would have worked better:

Another dark psychological secret magicians routinely take advantage of is known as change blindness — the failure to detect changes in consecutive scenes. One of the most beautiful demonstrations is an experiment conducted by the psychologist Daniel Simons in which he had an experimenter stop random strangers on the street and ask for directions.

Midway through the conversation, a pair of confederates walked between them and blocked the stranger’s view, and the experimenter switched places with one of the stooges. Moments later, the stranger was talking to a completely different person — yet strange as it may sound, most didn’t notice. 

I wonder how much of a change I could get away with.. Will it matter how long of a conversation? Game sessions are a bit more involved then a conversation on the street. So I would think that they would detect the change. May have to setup a game to test this idea..