Why Does Moving Desk Cause So Much Confusion?

Today in class the room was set up for a socrative type discussion for the AP Psychology class. While in the regular psychology/sociology class, they were not doing that activity, they were starting on group projects, so they have something to do the next day while Ms. Hollenbach was not there. 

Hollenbach called right before the students walked into the room, "There is going to be a lot of chaos in the next class because the seats are different. They won't be sure what to do." Sure enough not a moment after, the first student walks in, looks at the room with growing wide eyes and utters, "Uh..." "Just find a seat." Is the answer, and the continuous answer as the rest of the class files in.

Why is it so confusing for students if there is something as simple as a desk change? Understandably, there is something the students themselves don't know about, they like routines. They like the same thing the same way everyday. This may be attributed to the factor that students need to feel a sense of safely, and routes provide a layer of that. So even altering a routine, such as the way the desks are set up, may cause a bit of a scuffle.

But that doesn't fully answer the question of why when something such as setting gets change, their concentration and common sense may be left outside in the hallway. What do you think is the reasoning?