This unfortunately would seem to be a weakness with the Magsafe system. Even though the magsafe port & magsafe connector on the cord seem to be designed to minimize larger pieces of metal from interfering/cross-contacting 2 or more magsafe pins...I guess nothing is perfect & it can happen.
I've actually had some similar concerns with my MacBook Air. Unlike my MacBook Pro's...on my MacBook Air...one of the USB ports is right next to the MagSafe port. And since the USB connector is similar in shape & size to the magsafe connector...I have a few times (without looking) accidentally tried to plug a USB device into the magsafe port.
The USB cable connector fits perfectly inside the opening for the magsafe port...and when the metal USB connector gets close enough to the magsafe port...the strong magnet inside the magsafe port will "pull" (via magnetism)...the metal USB connector right into the magsafe port.
On the positive side...it would seem that this is a VERY rare event.
Since this is the very first time I've ever heard someone's Apple portable computer get damaged in this way. I'm sure if I scoured the internet...I could find more examples...but in everyday interactions with Apple users (in person or internet forum)...this is the first time ever hearing of this.
Sorry to hear your MacBook Pro got damaged iggbar
...definitely a great reminder to all of us to be VERY careful with metal around a magsafe port or magsafe cord connector!
Thanks,
- Nick