Dan Frakes notes if you’re traveling with your iPad and a Bluetooth keyboard, and you use the iPad Passcode Lock:
Make sure you turn off the Bluetooth keyboard before sticking it in your bag if you want to be able to use your iPad when you reach your destination.
Otherwise, as Frakes notes here:
If you forget to turn off your Bluetooth keyboard, or to disable the iPad’s Bluetooth, before tossing your gear in your bag, chances are you’ll arrive at your destination with an iPad in lockout mode. The keyboard’s keys will get pressed in transit, those key presses will be interpreted by the iPad as attempts to enter your passcode, and unless your luck is very good, those attempts will all be wrong.