I'm bad at judging size based on weights, but I agree a mouse would have a tough time really doing harm to a larger BP in 30 min. unless it started in somewhere like the face or cloaca. It's just not that easy for a mouse to break the skin on most of the snake's body.
That being said, I'd never leave a mouse alone with my snake for even a minute. On the offchance it started doing damage I'd never forgive myself.

In the future if you decide to leave a rodent in with your snake (even if it's a low risk, I just can't bring myself to recommend it in any but the most desperate situation), make SURE it is well fed and watered before hand. Maybe even leave water and something for the mouse to nibble on in the tank. A hungry/thirsty mouse is a lot more likely to get curious about what your BP tastes like.