I did the equivalent of this when traveling and I left my IP packet at the hotel. I stopped and bought a Pure Protein bar, which is the equivalent of a restricted. I had already had ridges on the train... so basically had two restricted...
I did it one day, and it didn't impact my loss for the week. If you are in a sticky situation, doing this is probably better than an out-and-out cheat. However, like Jordana said, it might kick you out of ketosis. People have varying degrees of sensitivity to carbs, and some get kicked out more easily than others.
See mini goal album for weekly weight losses.
~ 170s 5/2
~ 160s 5/30
~ 150s 7/11
~ 140s 8/15
~ Goal 9/16
If I do what I have always done, I will look like I have always looked and weigh what I have always weighed...
This diet/protocol/way of life that we call IP is a way out... if you let it be.