Please note: this was a hardware issue, as I suspected from the beginning. I posted here to find out if others had similar experiences, as it appears they did. Please don't continue to offer suggestions for resolving the issue. I assure you, they will not help. My home button died over the weekend, so last night on the very last day of my AppleCare+ coverage, I walked into the Apple Store for a Genius Bar appointment and walked out with a brand new (manufactured Week 37 2013) iPhone 4S free of charge two years to the day after I purchased my phone. Thanks Apple! HOWEVER, about two hours after I got the phone home, after performing an OTA upgrade to 7.0.2 and in the middle of restoring from my iCloud backup, my WiFi suddenly died. No networks detected, settings button on "off" and grayed out so it can't be turned on. Reset the phone, the network settings, did Erase All Contents and Settings (the Setup Assistant didn't even offer to connect me to a WiFi network), restored the phone three times. Set up as a new phone. No luck. Always grayed out. Even did online chat with a service rep, who had me restore yet again. No dice. It seems to be a hardware issue (maybe a baseband firmware issue?). I have another appointment at the Genius Bar tonight. Has anyone else experienced sudden, irreversible loss of WiFi on the iPhone 4S or after upgrading a phone to iOS 7?