You have to be a little more specific. You're trying to install this app from the Apple Appstore? do you get an error? it just disappears? what happens? Is it Tango Video Calls? If it is I just installed it on my JBen iPad.
I tried to install it from the AppStore on my phone and from iTunes. When I press install it takes me back to the home screen as it normally would do but I didn't see the app itself installing. Nothing happened. And yes it was tango video calls
how many screens do you have? for some reason even though you might only have one screen on your phone with lots of space any new apps automatically go to the second screen. So try swiping to the right to see if the icon is there. Also when you connect up to iTunes and go to the App section under you iPhone do you see it in the list?
can you think of anything you installed at the same time or after you installed it? What happens when you try searching for it in the Finder? Do a search for disappearing icons I can't remember the app that caused it since I don't use the app. There's no use blindly uninstalling Cydia apps unless you only have a few. If you think it's the theme turn it off and respring. Do you have SBSettings? go to more then App Folders and look for this on and tap it. This will give you the folder path which will definately tell you it's installed.