IPhone replacement/ smashed screen?

I have an iPhone 4, and the screen is smashed. Earlier this year i smashed the back screen and the apple store replaced it free and quite happily. But the problem is, that i was with my mum then and i don't know whether it had anything to do with insurance or something? So i'm going to the apple store on monday and i don't want to tell my mum the screen is smashed, so i want to know whether i need to take any paperwork?

It could be an insurance thing. However the back panel is far easier and cheaper to replace than the screen itself is, and that could be the difference here.

Since she will find out anyway, I would just own up to the problem and let her know, rather than try to sneak that behind her back.