[Pharmboy]

The Patriots could not get to them until after the war, and that was 7 years later when there were—evidently—no signs of the mass grave. The Brits occupied all of NYC for the entire war, including Brooklyn, which did not actually become part of NYC until 1898, I believe.

[Pharmboy]

The article mentions two possible places for the burial site: 1st Street and the Carrol St Bridge, and 9th St between 1st and 2nd Avenues. See the map here to see those places on a map of Brooklyn. And the "Cobble Hill" area is named after the hill that was cobbled together by (mainly) Massachusetts soldiers in order to make some high ground.

And one more thing: the article says that the Battle of Brooklyn was the first major battle of the war. That's true only if you discount Bunker Hill, which I cannot. It was the largest (largest number of soldiers...around 28,000 from both sides, mostly Brits and Hessians) battle of the war...that stood for all time.