And now, I have a cause of action against the airline, for deliberately taking my secured weapon away from me and handing it over to law enforcement. Furthermore, it might be impossible for me to recover that property, since the state where the firearm was found might have local licensing laws (e.g. NY) and I might not have, or be able to obtain, a license in that jurisdiction.

In any event ... I still think the airline comes across much worse in your scenario ... which is why the airlines seem to take so much more care with luggage containing declared firearms. (Which was, after all, the original point of the thread ...)