You can't restore to iOS 5.1.1. And re-restoring using RedSn0w is the only way to go back to any iOS 5 versions since it takes advantage of a restore process exploit that's in iOS 5 for the iPad 2 and iPhone 4S, it won't automatically jailbreak it for you. RedSn0w's not only for jailbreaking, it has other uses as well. Since you don't have a 5.1.1 listed on the top of Cydia, you cannot restore back to iOS 5.1.1 by any means, and your only option is to upgrade to iOS 6.0.1. You can manually delete everything off the phone itself, but the jailbreak stays unless you remove it with developer access to your device.