Call me a skeptic on this one.
I have never seen carb ice that did not clear simply by applying full carb heat. The engine may stumble for a bit but it will pick up quickly so by the time you finished faffing around with the mixture the ice will be gone anyway. I live in a temperate Coastal city that has conditions conducive to a very high probability of carb ice for at least 6 months of the year.
The signs of carb ice are clear if you are looking for them starting with a uncommanded reduction in power followed by rough running. There is simply no excuse to let the engine develop so much ice that it stops.