Are you sure they deleted it? perhaps they moved it to the second screen? scroll to the next screen and see if its there or in a folder, go to your search and type in "settings" and it will come up.
Sorry Rug just saw your post
You can still swipe to the far left, type in "Settings", and it'll be found right there. What you can do from thereon within Settings is go to General > Reset > Reset Home Screen Layout. This will reset all your icons on your home screen to their default positions.
Isn't it possible to connect the phone to iTunes, click on the phone, go to the Apps tab and locate and rearrange the installed apps to your liking? I'd never allow my kids to play with my phone that way. Get them an iPod Touch.