Please, follow the instruction from MSDN: Remove or Delete an Item or Project - SQL Server | Microsoft Docs
Quote:To remove a project item:
- In Solution Explorer, select the project item you want to remove.
- On the Edit menu, click Remove.
- On the confirmation dialog, click Remove to remove the item from the project.
A removed item still exists on the file system. Therefore, you can add a removed item to its original solution or to another solution.
IF you can not locate file and you're able to see it in the left pane, go to:
Tools->Options->Projects and Solutions->Track Active Item in Solution Explorer
If above is inaccessible, follow the instruction from: Visual Studio Tip #8: Adding existing files with Show All Files – The Brain Dump
Then you'll be able to remove that files from solution explorer.
Finally, you can always show all files: Solution Explorer doesnt show the folder although the folder is present in my local drive (local copy) Visual studio - Stack Overflow