Sometime many command menu items disappear suddenly , to fix this try to reset the Visual Studio Settings if you loose one of the needed item.

To Reset the Settings follow this steps :

1. On the Tools menu, click Import and Export Settings.

2. On the Welcome to the Import and Export Settings Wizard page, click Reset all settings and then click Next.

3. If you want to save your current settings combination, click Yes, save my current settings, specify a file name, and then click Next.

   —or—

   If you want to delete your current settings combination, choose No, just reset settings, overwriting my current settings, and then click Next. This option does not delete default settings, which will still be available the next time you use the wizard.

4. In Which collection of settings do you want to reset to, select a settings collection from the list.

5. Click Finish.

   The Reset Complete page alerts you to any problems encountered during the reset.

Source:  How to: Reset Your Settings @ MSDN

Another way :

use the devenv /resetsettings Visual Studio command MSDN