Accidentally deleted that app you really need? Here are three possible ways to recover it.
Your application may be in the Recycle Bin (Windows) or Dustbin (Mac).
On Windows, go to your desktop and double click on the recycle bin to open it.
On Mac OS X, click on the dustbin in the dock to open it.
If you see the application, drag it onto your desktop and double-click on it to reinstall it. Otherwise, try another method.
Your application may also still be in the iTunes application storage folder. To get there, right-click on another iTunes application and click on "Show in Windows Explorer" or "Show in Finder."
Look through the "Mobile Applications" folder for the missing application.
If you see the application, double-click on it to reinstall it.
If the above methods don't work, you can always redownload the application from the iTunes store. First, open iTunes and click "iTunes Store" in the sidebar.
Search for the application you want to download again in the search box.
If it is a paid application, make sure you are signed into the iTunes account that originally bought the application by using the "Store" menu.
On the application's store page, press the either the "Get App" or "Buy App" button. If it is a paid application, iTunes will say that you already bought that application, and you can download it again for free.
Click OK, and it should begin to download.