Accidentally deleted camera app?

My dad somehow accidentally deleted his camera app on his iPhone 4… I have no idea how it happened but it did… He can still use the camera through the thing on the lock screen but there's no app once he unlocks the phone… Anyone know how to fix this?

Thats impossible.

Apple stock apps are un-deletable unless this is a jailbroken device we're talking about.

Well the camera is un-delete able without jailbreak so check if he moved it to a folder or something but if you have jailbreak just download this app from your iphone
https://itunes.apple.com/...03072?mt=8
or just get a similar app