No problemo... going to see what Apple can do for me.. you never know.
There is no consistency to throwing a phone into a pocketbook. Out of the thousands of times your wife through her 3g into her purse maybe this time with her 3gs it hit just perfectly on something jagged or sharp. There are tons of variables taking place. A bag full of different size and shape objects. Placing the purse down lightly..accidentally dropping the purse on a hard floor pushing another hard object into the screen of your phone.. All at the right place and time causing a scratch in the glass.
The coating is just a thin chemical bond to the glass. It is still the same 3g glass underneath the coating. if the glass scratched through the coating then the screen hit something hard enough to do it whether it would be your old 3g or a 3gs. Just because it didn't happen all those times in the past doesn't mean it couldn't hit just perfectly on an object this time causing the scratch.
It's almost like you have driven down the same road for 10 years to your job and all of a sudden on one day you happen to run over a nail in the street. It never happened before with the same tires..why now? It's just the random unpredictability of life.
In the end it's just a cell phone.