I think if the OP was drying his briar on Mercury it would be damaging, but setting it in a sunbeam for a while I'm sure wont have adverse effects.
Why you would want to leave your pipe in the sun is beyond my comprehension
If you followed this logic, why you would make a small fire inside a pipe bowl?
Why is it that when you take a piece of wood(something found in nature) and carve it into the shape of a pipe, it some how turns it into something less durable than an old piece of wood.
People posting here with questions like this, or "OMG, I left my pipe in the rain what am I going to do?".
Everyone needs to remember it's just a piece of wood, and wood has been exposed to the elements since the beginning of time.