Re: my camera on the htc m one 9 has disappeared how do i get it back
Disappeared from the app drawer? There are a number of free camera apps, most of them better than the one that comes with any phone. Install A Better Camera, Camera FV-5 Lite, Open Camera and a few others and you'll see.
If it just disappeared from the homescreens, open the app drawer, long-press it and drag it to the homescreen you want it on.