I'm a noob but I had a similar issue with YouTube when I upgraded to iOS 5. The icon simply went away. I restored from iCloud with no joy. Reset to factory defaults and still no joy. Someone sent me an email with a YouTube link that I watched an lo and behold my YouTube icon reappeared. I chalk it up to smoke and mirrors. I know this doesn't help you with your problem but you're not the only one seeing anomalies.......
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