Missing Application Folder

If the name is already taken, then the folder must still be there. Try doing a Finder search of the hard drive or download the third-party search utility Easy Find and search for the folder. You may have just moved it.

If you put it in the Trash but have not emptied the Trash, then you can simply drag the folder back to it's normal location.

You cannot 'accidentally' delete the Applications folder because if you try to send it to the Trash you will see a pop-up dialog requesting your password in order to delete the folder. An actual deletion of the Applications folder must be deliberate.

Download the utility Show Hide Invisibles. Use it to toggle visibility of invisible files. See if your Applications folder shows up. If so then re-toggle invisibles OFF. Hopefully, you Applications folder will remain visible.

Is it renamed as '.Applications' with a period in front of the name? If so rename it by removing the period. If this is not the case then download the utility File Buddy that you can use to make the folder visible.