First of all, I'm not going to beat a dead horse because people have already given you some great advice.
I would, however, like to know what you are feeding the snake (as in what size) and are you sure it was only in there for 15 min? Usually, feeding smaller live meals in safer and make sure your feeders have food and water before being fed to your snake. If you get your feeders from a pet store, they can be cramped without food or water. Making sure the feeder is calm, well hydrated, and not hungry will help you against attacks. In addition, if you monitor your feedings (by keeping the tub open unless you have a nervous snake who won't eat while you're watching) and have a set of tongs/a pencil/chopstick/etc to put between the rat's teeth and your snake, feeding live can be very safe. I feed all my ball pythons live (minus one hatchling) and I've never had an issue with a rat attack.
Now, I'm not going to discourage you from switching off of live, but I just want you to be informed so you're switching for the right reasons. Feeding F/T can be just as safe and/or dangerous as feeding live.