If they got on it just as it was coming up and 1-2" tall and it's completely gone now, I'd say definitely army worms. We sodded roughly 25 acres of bermuda on a range job at Eglin. Got it established and fertilized. Looked gorgeous, lush deep green, thick enough for a golf course when I checked it on a Thursday afternoon. Came back toward the middle of the following week and there was nothing but brown stems about 1/4" tall as far as the eye could see. Never underestimate how quickly army worms can eat up an area. Like I said, 25 acres pretty much completely gone in less than 6 days.
