If you put an uncrustable sandwich under a hairdryer will it thaw faster?

No. It will just dry out the outermost layer. The inside won't get any heat, or won't get enough heat fast enough to do anything to thaw it. A hair dryer isn't all that hot, really. It's just hot enough to dry hair, not thaw or cook food. In a worst case, you might just heat up the sandwich enough to encourage bacteria to grow. There's an optimal, low temperature (like 100-120 degrees) where it's not safe to keep foods because of it being a very favorable temperature to grow bacteria.