A good friend of mine Mike Bell had a similar fire 2 years ago that destroyed 10 of his cars and all his signs and memorabilia. The building was the only thing he had insured unfortunately and has since been rebuilt. He has also started to rebuild his collection, this time insured. It was later determined to have been started by a lightning strike.
http://www.sj-r.com/article/20140403/NEWS/140409712