Hi mate. Did you loose all the coolant and also did you notice what sort of temps it got upto before you pulled over? Usually when your light flashes you've lost coolant, but looking at your original post again, it reads that you drove it with the coolant light flashing for 20 minutes before the pulley let go? you could have warped the head if temps got too hot... Also, what mileage has the car done, and any indication if head gasket has previously been done? It's unfortunate that it happened so soon after purchasing, however water pumps can fail anytime, without any prior warning so unlikely