It would surprise me if Jagex forgot to add one, but then again, Jagex has done some weird stuff here and there. Could it be that you already entered your bank PIN to access your bank or GE before you opened your ore bank? The bank PIN is normally shared over all storage things, and entering it once when opening one of these storage things, will make it work for all the other storage things if you open them during the same login session as you already showed that it was really you.
If a bank PIN is enabled, and the ore bank doesn't ask it when you haven't entered your bank PIN before in that session, it should definitely be changed so the ore bank does ask it.The RS Wiki needs a hand, and Bwian's will gladly take the rest of your body!
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