I wonder if the severity of the burn was the reason it did not stop the pain immediately. Maybe the length of time from the burn until application. I have used WW for several years and had total success when applied to burns. On different occasions my wife and a 10 year old granddaughter burned their fingers on a hot stove burner. In both cases WW was applied full strength and the pain was gone immediately. 3 years ago an ice storm had us without electricity for 3 days and I was using a portable heater that screws onto a tank of propane. I burned my arm and the application of WW stopped it immediately also. In all these cases the burns was not a deep burn that goes down more than one layer of skin.
I also use WW for many things and I buy it by the gallon. I do love this stuff.