If I remember correctly, Holgrave in The House of the Seven Gables said that daguerrotypes reveal true character. the process takes a long time so people cannot hold a false expression. They always revert to their natural state.
So there always was a cave used for crime fighting equipment, it just was not called The Bat('s) Cave until the serial. What else would you call an underground chamber large enough to hold an airplane even if it is of human origin?
http://lightupicecubes.net/
Their conclusion is as valid as saying that humans do not need all of their fingers.