The specific scenario proposed might be a temperature drop due to the precipitation of the pre-Flood canopy or a cometary ice dump. To answer these questions, we must first establish the facts, checking the original sources. And when we do, we find that no more than several dozen mammoths have been found frozen or partially frozen. It is true that tens of thousands of mammoth bones are found, and mammoth ivory has been mined commercially in some places, but those were not quick-frozen. The frozen parts, are, with few exceptions, found in the frozen banks of modern rivers, usually in small lenses within the larger tundra layer.
Some specimens seem to have drowned after breaking through ice covering a river.
The frozen meat itself, while wolves and sled dogs have been known to sample it on occasion, is usually somewhat rancid, not quick frozen and ready to be sold. The soil and the carasses couldn't have floated around for months while other sediments were deposited, especially in a quick-frozen condition. These creatures seem to have been well suited to an Ice Age climate, but not well adapted to an ideal pre-Flood world. In the early years after the Flood, there would have been few predators of large animals, and enough vegetation to support large herds. An interesting comparison could be drawn with the elk population on Mount St. Helens following that catastrophic destruction in 1980.