did i kill my van?

i (accidently) drove my van (automatic transmission) on the highway for about 25 miles with it in 3rd gear. started smelling like it was overheating and could hear radiator sizzling. then noticed i was loosing speed and tried giving it more gas and it just continued to slow down. suddenly realized that i had it in the wrong gear so i put it in drive and it instantly died. i coasted to side of road and white steam was coming out under the hood. i tried to restart it and it cranked but would not start. it also sounded different when cranking, like a higher pitched sound than normal. got a ride home, and husband went back with me a few hours later. it still won't start, just cranks. (he brought water to put in radiator, it was completely dry.
did i blow up the engine? can it be fixed?