Open the camera by pressing the side button twice, while in the camera go into recent apps, tap on the camera icon and go into settings, clear the cache and data and force stop it then restart device
How did you "lose" the icon? Is it that the icon is no longer on your homescreen? Or is it that you still see an icon for your camera just not the usual camera icon? Also remember to tap on reply so the person helping you gets notified that you have responded.
You should be able to touch and drag it to the homescreen from your app drawer. Touch it hold and then drag it to the top. The homescreen should pop up and then you can place it there.
Maybe the homescreen layout is locked? At the homescreen touch and hold on an empty area. Settings should come up. Look for lock homescreen layout and be sure that is off.
