iPhone 4s broken camera

My iPhone 4s camera wont work, either the shutter stays closed or its a black screen, but my face time works. This problem has occured ever since my lock button broke. I made an appointment with the genius bar, and after dealing with a rude employee, they told me it was due to lack of memory even after I tried to explain to them that my camera worked even when my memory was full. I deleted all of the videos and pictures off my phone and I have 7MB of empty space. My camera still did not work. I backed up and restored my phone on iTunes, this also did not work. I have restarted my phone and this didn't work either. Any suggestions as to what the issue may be?