I have tried Google, and all so many discussions, and almost none helped. After deleting an entry from the Applications menu, which can be done from the menu editor opened by right clicking the Ubuntu Icon, and selecting 'Edit Menus.'
I deleted a few entries which were visible even after the application had been uninstalled. After reinstalling the applications, I failed to see them reappear.
From my experience, the entries are never deleted, but merely removed from the menu, and are blacklisted. So even after installing the application, they fail to appear in the menu.
After a little search, I was able to find the links in ~/.local/share/applications where ~ represents the user's home directory. I could find all the application links that I had deleted.
The simplest way to get them back is to drag them to the menu editor.
I will investigate and post once I have more info.