On my iPhone I purchased the MotionX-GPS app to keep a GPS log of my vacation travels. Since this drains battery a bit, I dug up an old iPhone 3G and restored it to factory settings and signed into the iOS App Store with my Apple ID. For some reason, when I search for the app in the App Store it does not say "Install," which is what I believe it should say since I have already paid for it on the same account, but instead it lists the app price. I'm running iOS 5 on my iPhone 4S and iOS 4 on the iPhone 3G that I want to use exclusively for running this app I've already paid for but apparently have to buy again unless I'm doing something wrong. Thanks for your help!