OK. I've put it in same pocket with same keys for hours and I have been walking home for 30 minutes. No more scratches so far, just that tiny one! Now I'm 99% sure it is a factory scratch.
I don't know if I can take it back to att store and change for a new one, but if I have to wait another 2 weeks I'd rather live with it.
Well since you went through such extreme testing procedures and came up with your completely accurate 99% sure result, I guess we have no choice but to agree with you and stop believing that your metal keys could have possibly scratched your glass phone.
Seriously, Ever since the 3G, my iPhone has NEVER been in the same pocket as my keys. It's called common sense man, I know some people here have to have it.