Where can a program disappear? Pinterest is gone.

Apps can be removed from the home screen without being deleted. Go to the App Library (swipe left past your last home screen). From there you can touch and hold an app and slide it left back to the home screen.

If it was deleted, it can be reinstalled from the App Store.

Our Pinterest also disappeared a couple of weeks ago from our Mac Desktop. I've tried numerous ways to fix it and one board returned but only partially. Pinterest is fine and everything is there on my 10 year old laptop and my newer iPad. What happened on our desktop???