remove scratch from iPhone 5 front glass
Yes, probably the rivets from your jeans.  I've done that before.

A screen protector is always a good idea because of the time and money involved in replacing the touch screen.  Especially for any of the iPhones; they are expensive.  I have always loved the screen protectors from Screenguardz.  Compared to the ones at Best Buy (forget which brand), they are extremely smooth and the anti-glare is great.  Here's the one for the iPhone 5...

ScreenGuardz - iPhone 5

Also, if you already have scratches in your touch screen since you didn't have a screen protector there in the first place ( duh, :D just kidding), you might check out the compound from these guys.  It looks like industrial grade stuff or something of the sort.

TDI Smart Technologies - Glass, Acrylic, and Gorilla Glass Compounds