Lock the screen orientation
Double-click the home button to bring up the multitasking interface, then swipe from left to right. Now tap the portrait orientation lock once to turn it on and again to turn it off.
Locate your Lost iPhone
Well I hope you never have to use this but just in case there is an app (of course) that will help you locate your lost iPhone. Find My iPhone can help you locate it on a map and protect its data. You can even initiate a remote wipe to delete your data if you feel you need to. For instructions on how to set this up, visit find my iPhone setup.