It would have let you create a custom wallpaper to use as your iPhone's "locked" screen that had contact information you chose. An email or phone number you provided would have been easily visible if your phone was found, even if a passcode lock is used.
It would have protected your privacy too--without it, even a good samaritan would have to search your contacts, email, or your apps to find where to return your lost iPhone. You even could have chosen from several built in backgrounds, picked any image from your photo library, or taken a photo right within the app.
While it is a shame, it's honestly not a surprise. We were hoping the reviewers might have a little sense of humor in this case--but it's probably a pretty touchy topic within Apple. When I saw "Apple Inc" on the caller ID, I figured that's what they were calling for :)
But there is good news! Thankfully, it is already in the App Store with the name "Reward for Return". It's been there since last June. If it had been used on a certain lost iPhone, it might have saved a lot of trouble for a lot of people.
As an aside to the finder of the lost iPhone...did it never occur to you that Apple (with billions of dollars at stake) might have given a pretty nice "thank you" to get their device back and to keep the whole thing quiet and private?