So I tried to activate Siri on my iPhone and I got the message, "iPhone unavailable. Please try again in 5 minutes." At first, I was puzzled, but then I remembered that this might be a passcode issue. So I figure that the screen was accidentally on, and the phone was in my pocket with my eyeglass case, and this somehow resulted in some incorrect button presses. Apparently, Apple temporarily locks you out if you incorrectly enter the passcode too many times. It is a security feature. This would be bad if there were an emergency, although during the lockout it gives you the option of making an emergency call.