I have had two iPhone 4's for the past 2 years. One I bought for myself, the other was given to me by my employer.
On my personal phone I installed screen protector film from day 1.
On my work phone I did not install a screen protector.
Both are kept in the same pants pocket and are exposed to the same daily wear and tear.
To this day, my personal iPhone 4 screen is still scratch free under the film. My work phone, on the other hand, has incurred a 1 inch curved vertical scratch at the top of the screen.
So when I got my new personal iPhone 5 the first thing I did was install screen protection film.
The phone screens are made of GLASS, not diamond or sapphire. They can and WILL scratch.
Good luck getting Apple to comp a replacement for your personal mishandling...