Another option is to delete the Unreal Engine version you’re using, and then re-add it, from the Engine Launcher.
This will re-install all files, which includes that mesh.
The draw-back is that it takes longer to download the code again 
Another option is to delete the Unreal Engine version you’re using, and then re-add it, from the Engine Launcher.
This will re-install all files, which includes that mesh.
The draw-back is that it takes longer to download the code again