When you loaded the os did you uncheck facebook? If you did you may be able to run the app loader. If that is no available you can reload the os but make sure facebook is checked.
Posted from my CrackBerry at wapforums.crackberry.com
You can just download twitterberry again from your BB browser. If the icon is missing and not just hiding that should solve why the option to upload is not there. Downloading it again should bring it back.