Your 15,000 er 1,500 dollar kite isn't useless with a bad nipple. It's a relatively cheap replacement part or you can use Aquaseal wetsuit repair glue to glue it back on. I just did this on my leading edge bladder on a Best kite that I've had for a few years, and I live in Florida.

Knowing that temps in my car can get extremely high in summer, I avoid storing my kite in my car unless absolutely necessary. I had a friend who kept his kites in his car all last summer so he could kite after work on his way home and he had numerous problems with nipples with kites of all brands. High temps + nipple valves = bad news.

Also, I believe the nipples are ultrasonically welded at the factory.