Hello. I have the 4s, version 6.1.3. various apps like the music (the music note icon) the clock, mail and others, keep disappearing from the main screen. The apps themselves are still in the phone and working. I can find them thru Siri or in the bottom panel (accessed by double-tapping the main button). It's annoying that I can't have them arranged how I want in the main screen for maximum accessibility. Please help! Thanks in advance. PS. I'd like to avoid updating the ios if possible.