The prevention of baseband upgrade shouldn't have caused this since it's not changing it at all whatsoever. Assuming your iPhone is still on 5.1.1 and has OpenSSH on it, theoretically if your iPhone had Wifi on before the whole incident, then you can SSH onto it. During a reboot of a device, SSH is automatically turned on. If Wifi was previously on, it will stay on, and you should be able to see it in your internet gateway's list of connected devices. Attempt to upgrade to iOS 6.0.1 yourself. Put it into DFU mode, and restore it using RedSn0w.
You shouldn't be getting the missing keys.plist if you're using the restore function in RedSn0w in Extras > Even More > Restore.