Nikon is slowly discontinuing Nikkor F-mount lenses and many products are still out of stock. The latest casualty spotted by mirrorless-camera.info is the Nikon AF-S Micro NIKKOR 60mm f/2.8G ED lens for F-mount – it is already listed as discontinued on the official Nikon Japan website and it is out of stock at Adorama and B&H Photo:
The full list of all discontinued Nikon lenses for F-mount can be found here.