Fascinating! I can't recall having seen or heard of this kit before. I do remember a Ferret kit, but it was an awful wood one from Sterling.
It's a shame the kit itself isn't available. On the basis of the instructions I can't tell how big it was - apparently pretty small. (Looks like the hull was molded in one piece.) The artwork the company commissioned for the instruction sheet is truly remarkable - especially so in view of how cheap the kit probably was. (The little Pyro sailing ship kits of the period, like the Golden Hind, Bonhomme Richard, etc., went for about 50 cents apiece.)
History-wise, the company screwed up rather seriously. The Ferret is a rather important vessel historically: one of the first documented warships built in the American colonies. But she dated from the colonial period - most definitely not 1812.
If scottrc is right about the same kit being marketed as a "Brig O War," the company really went off the deep end with its marketing ploys. The vessel depicted in these instructions has one mast; a brig, by definition, has two. "Independence Sloop" might actually not be such a bad label for the kit - though I don't think the actual Ferret lasted till the Revolution.
I do remember that one of the kits in that Pyro series - the ones with hull lengths of about six inches, that sold for 50 cents each - included something they called a "Brig of War." It was, if I remember right, a highly simplified and shrunken version of the Model Shipways Fair American kit. The proprietors of Model Shipways referred to Pyro as "Pirate Plastics." (Pyro also ripped off the Model Shipways designs for the revenue cutters Harriet Lane and Roger B. Taney, and the tug Dispatch No. 9.)
We tend to make fun of those old manufacturers from the 50s and 60s. The truth is that Ideal (aka ITC) was remarkably progressive and innovative in its choice of subject matter. The old ITC kits recently re-released by Glencoe are good examples. What company nowadays would do a "Billy Mitchell bomber," a Coast Guard surf boat, or a WWI subchaser? In terms of detail and accuracy they're hardly state-of-the-art, but it's tough to fault the company's choice of subjects.
Youth, talent, hard work, and enthusiasm are no match for old age and treachery.