Sony Xperia m4 aqua front camera icon gone

[AC Question]

Hi, the icon for switching between front and back camera has gone from my phone and I have no idea how to get it back. The camera was working fine in both modes but the phone kept saying low storage so I did clear cache on all of the apps to help this but since then the camera icon had just dissappered. I took it to the O2 shop and they just said to reset phone, which I've done and this still doesn't fix it. Any ideas? Thanks