It should work OK if you used it as you specified. Is the grass dry? Greener in the shade? Worse in the sun? Are you irrigating it properly? Did you actually use 1 gal per thousand, (or a bit more)? Was agitation adequate so that the mix and urea were fully dissolved?
If the solution burned it--you should be able to see a pattern of where the nozzles went, and when you made turns, starts and stops. Is this a Chemlawn gun? Flood nozzle? Back and forth with cone nozzle?