Okay Doug made the first point I always thing of when I hear people say carry a cell phone. That is if you do not have cell service then it is useless. Many people carry a cell phone with a false sense of false security.
Secondly the type of snow shelter mentioned of making a snow mound and digging into it actually takes a few hours to make as you have to let the snow consolidate after you pile it up, before you can dig into it. Also making a snow cave is VERY wet work. A snow treach is much better in 90% of the situations. Having equipment and know how to use it is the best of any sutuation.
cheers