AdrianW said:By iTunes I assume you mean the app on your Touch (not the app on your PC/Mac).
Has it by any chance moved onto the next screen? - How many white & grey dots do you have at the bottom of the screen? If it's more than one, then you have more apps on the next screen - swipe the screen sideways to drag the next screen into view.
If it's actually gone - then you should try a reset - hold the sleep button (on the top) until the Touch shuts down - then restart it. If that doesn't work, connect it to your PC and run iTunes and perform a restore.