Lost/Deleted Images on SD Card

Jul 9, 2018
I went out to shoot some photos and when I came home and put my SD card into my laptop, the photos were mysteriously gone and I put the card back in the camera, and they weren't showing up on that either. But when i was out shooting they were showing up just fine.

Any advice or reasoning to why this may have happened? And how could I recover the photos for free?

My camera is a Nikon D7200 and I have a SanDisk 32GB 45mb/s