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Welcome, I am Cory.
I am sorry you have lost the search box. Don't worry, it is not gone forever.
Right click on the toolbar/taskbar.
Click on Cortana in the menu.
Since it is not showing, 'Hidden' should be checked.
Click on Hidden and it should be showing again.
Let me know if this fixed the issue.
If it is fixed, please do not forget to rate my answer with 3 stars or higher at the top for assisting you today.