I guess you weren't quick enough to bring it inside. Just keep it indoors and hope it recovers. Brugmansia are not hardy at all.
http://treesandshrubs.about.com/od/commonshrubs/p/angelstrumpet.htm

Three years ago I lost mine to the 1st lightest frost we had, gutted as it had reached 6'. Anyhow, bought it into the unheated conservatory to over winter. The whole plant just died n dried right back to soil level, thought that was that but still gave it it's chance by not throwing it out & in the Spring new shoots appeared from the base, Hoorah !! Its now back up to 8'. It comes into the conservatory well before it turns cold now & is fine. Do remember all parts are poisonous ( it's Alkaloid ;-( but superb plants.

Make sure it's getting enough light and water, J. In a warm spot in the house, it can dry out in less than a week.