I've turned my laptop to Ubuntu a few hours ago, and, like usual, I installed a few programs, including TweetDeck. After I rebooted, I noticed that there were no shortcuts for TweetDeck anymore. I searched for it on Applications -> Internet, where isn't, and it is not even on my panel (where I put it after installation). It's not the first time I get this problem, so I've decided to report the problem to TweetDeck, hoping they have a solution (I searched through Google, but it seems that no one has reported problems like these with TweetDeck).
TweetDeck launches and works if I press "Launch TweetDeck" button on their website, so the installation is intact. I guess there are only some issues with shortcuts.If guys from TweetDeck will give me a solution, I'll post it here, even it will be to go where TweetDeck is installed and send from there a shortcut to desktop.
Update: I've talked to somebody from TweetDeck support team, and he told me that it sounds like being an issue with Adobe Air. He recommended me to reinstall TweetDeck, but since Adobe Air is managing it, I wasn't able to find a solution to uninstall it. I've just played a little with Adobe Air (just a few clicks inside it) and after I found TweetDeck into "Accessories". I don't know how it got there, what I know is that it was reseated in somehow, because that "welcome" window appears again (I set it when everything was normal not to open again).
So, I recommend you searching for the shortcut into "Accessories", and if you can't find it there, try to play a little with Adobe Air, eventually give it an uninstall, and then install it again.