just throwing this one out there, but driving it for a bit with a flashing engine light means that there was a pretty bad misfire, and since it was continued to be driven, a lot of fuel could have been dumped right through the cylinder and into the exhaust cause the cat to become completely clogged.
i had a cat completely clog up and it would not let the motor run for more than a few seconds before stalling out the car, if you let it sit for a couple of minutes, it would start right back up, run terribly, then proceed to die again.