I did a check amongst all of the collector insurance companies that I could find and all of them had several requirements in common: Locked garage, Over age 25, and own and insure another vehicle as primary transportation.
Good luck in your search
My guess would be also that if you were to claim a locked garage and not have a locked garage at time of claim, I don't think that thye would pay either, regardless of where the car was stolen from.
A search will lead you to a thread occuring about a month or two ago about that very same subject on turbo lounge.